Method for determining the density of a sheet of material using a magnetic force feedback actuator positioner

ABSTRACT

A density detection system uses a magnetic force feedback actuator positioner to maintain a precise selected pressure between transducer wheels and the surface of a sheet of material as the sheet of material moves through a position between transducer wheel and lift wheel. Consequently, the antiquated mechanical/pneumatic springs/airbags of prior art ultrasonic density detection systems are replaced with a highly responsive magnetic force feedback actuator positioner capable of providing a precise and relatively constant force that can react to the introduction of a sheet of material, and/or variations in the surface of a sheet of material, extremely rapidly without the bounce/recovery oscillations associated with prior art ultrasonic density detection systems. Consequently, precise density measurements of an entire sheet of material can be obtained with unprecedented accuracy.

BACKGROUND

There are numerous classes and types of wood products currently used ina virtually limitless variety of construction and other applications.Wood product types include but are not limited to: raw wood productssuch as logs, debarked blocks, green or dry veneer, and dimensionallumber; intermediate wood components, such as wood I-beam flanges andwebs; and layered wood products such as laminated beams, plywood panels,Parallel Laminated Veneer (PLV) products and Laminated Veneer Lumber(LVL) products.

One important physical characteristic for virtually every form of woodproduct is the density and resulting strength of the wood product. Thishas become an increasingly important parameter associated with woodproducts due to new regulations and standards allowing the use of newtypes of wood products and new uses of existing wood products forvarious forms of construction. In short, in order to put a given woodproduct to its best use, and thereby utilize natural resources mosteffectively, it is becoming more and more important to accurately andconsistently determine the density of a wood product and therebydetermine the strength of the wood product.

Layered wood products are one example of wood products that are nowbeing used in new ways and for more and more structures. Layered woodproducts such as plywood, PLV, and LVL are composite productsconstructed in a factory from both natural wood and one or morechemically blended glues or resins. They are manufactured on a productassembly line and typically fabricated from multiple layers of thinwood, e.g., veneer sheets, assembled with one or more layers ofadhesives bonding the veneer sheets together. These layered woodproducts, sometimes referred to as “man-made” but more commonly referredto as “Engineered Wood,” offer several advantages over typical milledlumber. For instance, since layered wood products are fabricated andassembled in a factory under controlled conditions to a set of specificproduct specifications, they can be stronger, straighter, and moreuniform than traditional sawn lumber. In addition, due to theircomposite nature, layered wood products are much less likely to warp,twist, bow, or shrink than traditional sawn lumber. Layered woodproducts can also benefit from the multiple grain orientations of theveneer layers and the resulting higher allowable stress capacities thana comparable milled lumber product. However, as discussed herein, toachieve this potential it is often critical that the layers, such asveneer sheets, making up the layered wood products are accurately gradedbased on determined physical characteristics such as strength/density,surface texture, and moisture content to produce a panel of desiredstrength, thickness, and visual appearance.

The use of veneer, and particularly veneer that has uniform qualitiessuch as consistent strength/density, allows layered wood products ofvarious dimensions to be created without milling a board of the desiredthickness or dimension from a single log or single piece of lumber.This, in turn, allows for much more efficient use of natural resources.Indeed, without the use of various layered wood technologies, such asplywood, PLV, and LVL, the forests of the planet would have beendepleted long ago simply to meet the construction needs of theever-increasing world population. In addition, since layered woodproducts are fabricated in a factory under controlled specifications,layered wood products can be manufactured to virtually any dimensionsdesired, including dimensions such as length, width, and height wellbeyond dimensions that can be provided by milling from even the largesttrees.

The use of veneer layers in some layered wood products, such as plywood,PLV, and LVL, can also allow for better structural integrity since anyimperfections in a given layer, such as a knot hole, can be mitigated byrotating and/or exchanging layers of veneer so that the imperfection isonly one layer deep and is supported by layers of veneer below and abovethe imperfection in the layered wood products structure. However, theseadvantages are again dependent on the veneer layers being inspected forconsistent features such as density and strength.

In addition to veneer, as mentioned above, the accurate measurement ofdensity and strength of numerous wood products is also highly desirable.In addition, it is often important to accurately measure the density ofmany non-wood products and materials as well. For instance, othermaterials include, but are not limited to, plastic extrusion panels,rubber belting, composite panels of any composition, uhmw plastics,plastic and wood laminated materials, and the like.

However, the currently used methods and systems for determining thedensity, and therefore the strength, of wood products, including veneersheets, and various other materials is antiquated and extremelyinefficient and ineffective in terms of the accuracy of densitymeasurements. This inaccuracy of prior art methods and systems fordetermining the density of material is due in large part to the ratherantiquated mechanical components used with prior art methods and systemsfor determining the density of material.

For example, one established method and system for determining thedensity, and therefore strength, of a sheet of material, such as a sheetof veneer or other wood product, involves the use of prior artultrasonic density detection systems commonly referred to as stress waveanalyzers. In their simplest form, prior art ultrasonic densitydetection systems convey a sheet of material, such as veneer, on aconveyor belt to a density analysis station. At the density analysisstation, the sheet of material is run between a rubber lined lift wheeland a transmitter or receiver transducer wheel including a transmittingor receiving transducer element. In this way a portion of the sheet ofmaterial is maintained or “pinched” between the lift wheel and thetransmitter or receiver transducer wheel.

Herein the term transducer includes either a transmitter, receiver, orboth. Consequently, the terms transducer and transmitting transducer canbe used interchangeably as can the terms transducer and receivingtransducer. Therefore, as a specific example, a transmitting transducerwheel can also be referred to generically as a transducer wheel and areceiving transducer wheel can also be generically as a transducerwheel.

Typically, a minimum of two transducer wheels, and two lift wheels, areutilized in pairs of transmitting transducer wheel/lift wheel and pairsof receiving transducer wheel/lift wheel. In some embodiments two ormore transducer wheels and/or lift wheels are used. The sheet ofmaterial is then conveyed by the conveyor belt between the transmittingtransducer wheel and lift wheel and the receiving transducer wheel andlift wheel so that a first portion of the sheet of material is incontact with the transmitting transducer wheel and lift wheel at thesame time a second portion of the sheet of material is in contact withthe receiving transducer wheel and lift wheel. The transmittingtransducer wheel and lift wheel pair and the receiving transducer wheeland lift wheel are typically separated by a precisely defined distance,often around six feet.

Once the first portion of the sheet of material is between thetransmitting transducer wheel and lift wheel and, at the same time, thesecond portion of the sheet of material is between with the receivingtransducer wheel and lift wheel, the transmitting transducer wheel emitsan ultrasonic signal (typically in pulses). By separating thetransmitting transducer wheel and receiver transducer wheel the definedfixed distance apart, an ultrasonic pulse transmitted into the firstportion of the sheet of material by the transmitting transducer wheelthen travels through the sheet of material and can be received by thereceiving transducer wheel at the second portion of the sheet ofmaterial by passing through the sheet of material between thetransmitting transducer wheel and receiver transducer wheel.

Since the distance between the transmitting transducer wheel andreceiver transducer wheel is known, the density of the sheet of materialcan be determined by measuring the time it takes the ultrasonic pulse totravel from the transmitting transducer wheel, through the knowndistance in the sheet of material, to the receiver transducer wheel. Thedensity of the sheet of material can then be determined based on thepulse travel time with shorter travel times indicating higher densitiesand longer travel times indicating lower densities. The correlation ofpulse travel time to density will vary from material to material.

Once the density of the sheet of material is known, this can be used todetermine a relative strength of the sheet of material with higherdensities generally equating to higher strength and lower densitiesgenerally equating to lower strength. The correlation of the density ofthe sheet of material to the strength of the sheet of material will alsovary from material to material.

As the sheet of material moves through the prior art ultrasonic densitydetection systems and the transmitting transducer wheel/lift wheel andreceiver transducer wheel/lift wheel pairs, multiple density readingsare captured at multiple locations along the sheet of material, such asveneer. A reading taken every one to two inches along the sheet ofmaterial is common.

FIG. 1A is a photograph of a perspective view of a specific illustrativeexample of a prior art ultrasonic density detection system 100 showingseveral key components of these prior art systems. Seen in FIG. 1A areprior art support frame 101; prior art pneumatic supply system 107;prior art control panel 106; prior art pneumatic position systems 108;transducer wheels 110; lift wheels 141; and gaps 151 between transducerwheels 110 and lift wheels 141 in the “home” position.

FIG. 1B is a simplified block diagram of a side view of the prior artultrasonic density detection system 100 of FIG. 1A as viewed in thedirection of arrow 120A or 120B. FIG. 1B shows several key componentsbefore a sheet of material, such as veneer, is fed into prior artultrasonic density detection system 100. FIG. 1C is a simplified blockdiagram of a side view of the prior art ultrasonic density detectionsystem 100 of FIGS. 1A and 1B showing several key components of theseprior art systems as a sheet of material, such as veneer, passes throughprior art ultrasonic density detection system 100. FIG. 1D is asimplified block diagram of a side view of the prior art ultrasonicdensity detection system 100 of FIGS. 1A, 1B, and 1C showing several keycomponents of these prior art systems as a sheet of material, such asveneer, exits the prior art ultrasonic density detection system 100.

As seen in FIGS. 1A through 1D, prior art ultrasonic density detectionsystem 100 includes: prior art support frame 101; prior art pneumaticposition system air bag 103; prior art counter balance spring 105;transducer wheel 110; prior art traditional transducer lever arm 111including transducer support 113, transducer lever arm horizontalcomponent 115, transducer lever arm pivot point 117, and prior arttransducer lever arm vertical thickness measurement component 119. Alsoshown in FIGS. 1A through 1D are transducer lever arm stop 121; priorart transducer lever arm thickness/displacement sensor 123; conveyorsystem 131; sheet of material 133; prior art sheet of material detector135; lift wheel 141; and gap 151 between transducer wheel 110 and liftwheel 141 in the “home” position.

Of note again is the fact that FIGS. 1A through 1D depict either priorart ultrasonic density detection system 100 viewed in the direction ofarrow 120A or as would be viewed in the direction of arrow 120B.

FIG. 1E is a line drawing of a prior art ultrasonic density detectionsystem 100 showing several key components in more detail.

Referring to FIGS. 1A through 1E, prior art support frame 101 istypically made up of several beam and frame components. Typically, thesecomponents are made of stainless steel or a similarly solid, and heavy,material to provide support and a framework for prior art ultrasonicdensity detection system 100.

As seen in FIGS. 1A through 1E, prior art pneumatic position system airbag 103 is coupled to prior art support frame 101 and transducer leverarm horizontal component 115 of prior art traditional transducer leverarm 111. As also seen in FIGS. 1A through 1D, prior art counter balancespring 105 is also coupled to prior art support frame 101 and transducerlever arm horizontal component 115 of prior art traditional transducerlever arm 111.

FIG. 1F is a line drawing showing counter balance spring 105 of priorart ultrasonic density detection system 100 in more detail.

FIG. 1G is a line drawing showing prior art pneumatic position systemair bag 103 of prior art ultrasonic density detection system 100 in moredetail.

In theory, the purpose of prior art pneumatic position system air bag103 is to, in combination with prior art counter balance spring 105,provide a theoretically constant pressure on transducer lever armhorizontal component 115 of prior art traditional transducer lever arm111 which, in turn, theoretically provides a constant pressure ontransducer support 113 of prior art traditional transducer lever arm 111and transducer wheel 110. However, as discussed in more detail below,there are numerous, and significant, limitations on the ability of priorart pneumatic position system air bag 103 in combination with prior artcounter balance spring 105 to provide the theoretically constantpressure/force on transducer lever arm horizontal component andtransducer wheel 110.

As also seen in FIGS. 1A through 1E, prior art traditional transducerlever arm 111 is movably, i.e., rotationally, operatively coupled topivot point 117 such that prior art traditional transducer lever arm 111can rotate/pivot in either direction 116 or 118 about pivot point 117.As seen in FIGS. 1A through 1D, transducer wheel 110 is supported bytransducer support 113 of prior art traditional transducer lever arm 111at rotating center hub 112.

Also seen in FIGS. 1A through 1E is transducer lever arm stop 121.Transducer lever arm stop 121 prevents prior art traditional transducerlever arm 111 from pivoting too far in direction 116 such thattransducer wheel 110 comes in contact with lift wheel 141 when there isno sheet of material 133 positioned between transducer wheel 110 andlift wheel 141 (as shown in FIGS. 1B and 1D). Consequently, transducerlever arm stop 121 ensures a minimal gap 151 between transducer wheel110 and lift wheel 141. Transducer lever arm stop 121 is typically madeof urethane or a similar material.

FIG. 1H is a line drawing of a transmitting transducer wheel/lift wheelreceiver transducer wheel/lift wheel pair 110/141 of prior artultrasonic density detection system 100 shown in more detail before asheet of material, such as veneer, is fed into prior art ultrasonicdensity detection system 100, as is also depicted in FIGS. 1B and 1D.

FIG. 1I is a line drawing of a transmitting transducer wheel/lift wheelreceiver transducer wheel/lift wheel pair 110/141 of prior artultrasonic density detection system 100 shown in more detail as a sheetof material, such as veneer, passes through prior art ultrasonic densitydetection system 100, as is also depicted in FIG. 1C.

Also shown in FIGS. 1A through 1E is prior art transducer lever armthickness/displacement sensor 123 and prior art transducer lever armvertical thickness measurement component 119. Prior art transducer leverarm thickness/displacement sensor 123 is typically a laser-based devicethat measures the movement of prior art transducer lever arm verticalthickness measurement component 119 when a sheet of material, such assheet of material 133, moves between transducer wheel 110 and lift wheel141 (such as is shown in FIGS. 1C and 1I). The movement of prior arttransducer lever arm vertical thickness measurement component 119 when asheet of material, such as sheet of material 133, moves betweentransducer wheel 110 and lift wheel 141 measured by prior art transducerlever arm thickness/displacement sensor 123 is then used to determinethe thickness of the sheet of material, such as sheet of material 133.

Also shown in FIGS. 1A through 1E is prior art sheet of materialdetector 135. Typically, prior art sheet of material detector 135 isvision system that detects the presence of a sheet of material, such assheet of material 133, as the sheet of material moves towards themeasurement point between transducer wheel 110 and lift wheel 141.

Finally, FIGS. 1A through 1E include sheet of material 133 to beconveyed to prior art ultrasonic density detection system 100 byconveyor system 131. In various cases, sheet of material 133 is a sheetof veneer, a sheet of any wood product, or a sheet of any material thatis to be analyzed by prior art ultrasonic density detection system 100.In various cases, conveyor system 131 is any standard conveyor systemsuch as a traditional conveyor belt.

Referring to FIGS. 1A through 1I, in operation, sheet of material 133moves along conveyor system 131 to prior art ultrasonic densitydetection system 100. As seen in FIG. 1B, transducer lever arm stop 121prevents prior art traditional transducer lever arm 111 from pivotingtoo far in direction 116 such that transducer wheel 110 comes in contactwith lift wheel 141 when there is no sheet of material 133 positionedbetween transducer wheel 110 and lift wheel 141 (as shown in FIGS. 1B,1D and 1H).

Consequently, transducer lever arm stop 121 ensures a minimal, orequilibrium, “home” gap 151 between transducer wheel 110 and lift wheel141. In addition, prior art traditional transducer lever arm 111 andtransducer wheel 110 are in the neutral position and prior arttransducer lever arm thickness/displacement sensor 123 records thisposition as the zero, or baseline, position.

As sheet of material 133 moves past prior art sheet of material detector135, prior art ultrasonic density detection system 100 is triggered toreceive and to transmit ultra-sonic pulses to analyze sheet of material133.

Referring now to FIGS. 1C and 1I, as sheet of material 133 moves throughthe position between transducer wheel 110 and lift wheel 141, transducerwheel 110 is lifted up so that the gap 152 between transducer wheel 110and lift wheel 141 of FIG. 1C is greater that gap 151 of FIG. 1B,typically by a distance equal to the thickness of sheet of material 133.This, in turn, causes prior art traditional transducer lever arm 111 topivot in direction 118 around pivot point 117 as transducer wheel 110 islifted up. In addition, prior art transducer lever armthickness/displacement sensor 123 measures the motion of prior arttransducer lever arm vertical thickness measurement component 119 whenprior art traditional transducer lever arm 111 pivots and thismeasurement is then used to determine the thickness of sheet of material133.

As discussed above, and as shown in FIG. 1A, prior art ultrasonicdensity detection system 100 typically includes a minimum of twotransducer wheels and two lift wheels in pairs of transmittingtransducer wheels 110/lift wheels 141 and receiving transducer wheels110/lift wheels 141. As the sheet of material 133 is conveyed by theconveyor system 131 between the transducer wheels 110 and lift wheels141 a first portion of the sheet of material 133 is in contact with thetransducer wheel 110 and lift wheel 141 at the same time a secondportion of the sheet of material is in contact with the receivingtransducer wheel 110 and lift wheel 141. As noted above, the transducerwheel 110 and lift wheel 141 pair and the receiving transducer wheel 110and lift wheel 141 are typically separated by a precisely defineddistance, often around six feet. However, the accurate measurement ofthe distance is more important than the distance chosen.

Once the first portion of the sheet of material 133 is between thetransmitting transducer wheel 110 and lift wheel 141 and, at the sametime, the second portion of the sheet of material 133 is between withthe receiving transducer wheel 110 and lift wheel 141, the transmittingtransducer wheel emits an ultrasonic signal (typically in pulses). Byseparating the transducer wheel 110 and receiver transducer wheel 110 bythe precisely defined fixed distance, an ultrasonic pulse transmittedinto the first portion of the sheet of material 133 by the transmittingtransducer wheel 110 then travels through the sheet of material and canbe received by the receiving transducer wheel 110 at the second portionof the sheet of material 133 by passing through the sheet of material133 between the transmitting transducer wheel 110 and receivingtransducer wheel 110.

Since the distance between the transmitting transducer wheel 110 andreceiver transducer wheel 110 is known, the density of the sheet ofmaterial 133 can be determined by measuring the time it takes theultrasonic pulse to travel from the transmitting transducer wheel 110,through the known distance in the sheet of material 133, to the receivertransducer wheel 110. The density of the sheet of material 133 can thenbe determined based on the pulse travel time with shorter travel timesgenerally indicating higher densities and longer travel times generallyindicating lower densities. The correlation of pulse travel time todensity will vary from material to material making up the sheet ofmaterial 133.

As the sheet of material 133 moves through prior art ultrasonic densitydetection system 100 and the position between the transmittingtransducer wheel 110/lift wheel 141 and the receiving transducer wheel110/lift wheel 141 pairs, multiple density readings are captured atmultiple locations along the sheet of material 133. Some prior artsystems use belt speeds of up to three hundred and fifty feet per minuteand a density reading is taken every six inches along the sheet ofmaterial 133. However, this distance is typically determined by thespeed at which the sheet of material 133 is conveyed by conveyor system131 or the time interval between transmitted pulse, or both, andtherefore can be any distance desired. In some cases speeds of sevenhundred and fifty feet per minute can be accommodated using three ormore transducer wheels and some systems take a reading every inch.

Once the density of the sheet of material 133 is known, this can be usedto determine a relative strength of the sheet of material 133, withhigher densities generally equating to higher strength and lowerdensities generally equating to lower strength.

Referring to FIG. 1D, once the sheet of material 133 passes through theposition between the transmitting transducer wheel 110 and lift wheel141 and the receiving transducer wheel 110 and lift wheel 141, prior artultrasonic density detection system 100 returns to the starting/neutralpositions of FIG. 1B. Consequently, as seen in FIG. 1D, transducer leverarm stop 121 again prevents prior art traditional transducer lever arm111 from pivoting too far in direction 116 such that the transducerwheel 110 comes in contact with lift wheel 141 when there is no sheet ofmaterial 133 positioned between transducer wheel 110 and lift wheel 141.

Consequently, as seen in FIG. 1D, transducer lever arm stop 121 ensuresa return to the minimal/home gap 151 between transducer wheel 110 andlift wheel 141. In addition, prior art traditional transducer lever arm111 and transducer wheel 110 are in the neutral position and prior arttransducer lever arm thickness/displacement sensor 123 again recordsthis position as the zero, or baseline, position.

Most of the basic design and components of prior art ultrasonic densitydetection system 100 discussed above have not significantly changed inover forty years. Consequently, while prior art ultrasonic densitydetection system 100 can be used to gain a general indication of thestrength of a sheet of material, such as veneer, the accuracy andconsistency of the measurements obtained from prior art ultrasonicdensity detection system 100 are far from ideal. As discussed above, itis now often critical that a very accurate measure of thedensity/strength of a sheet of material, such as veneer, be made.Unfortunately, prior art ultrasonic density detection systems, such asprior art ultrasonic density detection system 100, often fail to rise tothe standards of accuracy and consistency required for newer materialsand structures.

It is important to note that the accuracy and reliability of densitymeasurements taken using prior art ultrasonic density detection system100 is almost entirely dependent on keeping a constant pressure ontransducer wheel 110, and therefore keeping the pressure/force oftransducer wheel 110 on the surface of a sheet of material constant. Anyvariation in this pressure/force will result in less accurate densityreadings, with larger variations resulting in larger inaccuracies. Usingprior art ultrasonic density detection system 100 this is problematicfor several reasons.

First, as noted above, the purpose of prior art pneumatic positionsystem air bag 103 and counter balance spring 105 is to provide atheoretically constant pressure/force on transducer lever arm horizontalcomponent 115 of prior art traditional transducer lever arm 111 which,in turn, theoretically provides a constant pressure/force on transducersupport 113 of prior art traditional transducer lever arm 111 and aconstant pressure/force transducer wheel 110 and the surface of thesheet of material 133. However, as a relatively antiquatedmechanical/pneumatic system, the accuracy and consistency of thepressure/force provided on transducer wheel 110 the surface of the sheetof material 133 by prior art ultrasonic density detection system 100 isnot only of questionable accuracy but is also highly inconsistent andsubject to significant and unacceptable error and interference.

When a typical prior art ultrasonic density detection system, such asprior art ultrasonic density detection system 100, is used to analyzesheets of veneer, prior art pneumatic position system air bag 103 iskept at a pressure of twenty-five to thirty PSI as read by a standardpressure gauge. Between inaccuracies in gauge reading and the physicalmake up of prior art pneumatic position system air bag 103, there isoften a three PSI or more error in the actual PSI and gauge PSI at anygiven time. Consequently, as an illustrative example, anytime the gaugereads a desired twenty-six PSI, the actual PSI can be anywhere betweentwenty two PSI and twenty nine PSI. This, in turn can result in avariance of twelve to sixteen percent in the actual pressure applied bytransducer wheel 110 or receiving transducer wheel 110 on the surface ofsheet of material. Of course, this can result in a significant variancein density readings from actual density from pulse to pulse in the samesheet of material and can result in a ten percent or more inaccuracy ofthe measured density of the sheet of material, in this case veneer. Forthis reason alone, prior art ultrasonic density detection system 100 isunable to provide the accuracy and consistency now required.

Another problem arises when the sheet of material 133 first enters theposition between transmitting transducer wheel 110 and lift wheel 141and receiver transducer wheel 110/lift wheel 141. When the transducerwheels 110 are lifted by the introduction of the sheet of material 133this “shock” can cause prior art traditional transducer lever arm 111 toover pivot, bounce back and forth, and cause transducer wheels 110 tobounce up and down, i.e., for gap 152 to be highly variable for a periodof time as an equilibrium position is reached. During thisbounce/recovery time, no reliable density reading can be obtained. Inmany instances, such as when the sheet of material is veneer, the sheetof material can be moving at a relative high rate of speed, as noted upto seven hundred and fifty feet per minute. Consequently, during thisbounce/recovery time, as much as ten percent of the length of the sheetof material 133 passes by while no accurate density reading can beobtained.

The problem arises because prior art ultrasonic density detection system100 is heavy, i.e., lots of mass and inertia, and being an oldermechanical/pneumatic system with no feedback provision, prior artultrasonic density detection system 100 cannot react quickly oraccurately to eliminate, or at least mitigate this issue. Consequently,the bounce/recovery time, and accuracy limitations are currently simplyassumed, and accepted as unavoidable, when using prior art ultrasonicdensity detection system 100. However, as noted, this level ofinaccuracy is no longer acceptable in many industries.

FIG. 1J shows a representation 170 of this bounce/recovery time problem.As seen in FIG. 1J, and FIGS. 1B and 1C, at time zero, the sheet ofmaterial 133 enters the space between transducer wheel 110 and liftwheel 141 and the transducer lever arm horizontal component 115 of priorart traditional transducer lever arm 111 and transducer wheel 110 arerapidly lifted from the transducer lever arm stop 121. This causes alarge displacement and bounce amplitude at 171 and 172. Then at 173 and174 through 175, 176, 177, 178, and 179, the displacement and bounceamplitude is eventually reduced. However, only at point 181, i.e., time30, does the displacement and bounce amplitude decrease to the pointthat a relatively accurate density reading can be taken. As noted, bythe time the amplitude oscillations decrease to the point 181 level, tenpercent or more of the sheet of material 133 has passed through thespace between transducer wheel 110 and lift wheel 141 and virtuallyuseless data is obtained about this portion of sheet of material 133.Clearly this is an unacceptable level of accuracy and consistency fortoday's demands.

Of note, as the sheet of material 133 moves through the position betweentransducer wheel 110 and lift wheel 141 past time 30, any irregularitiesin the surface of sheet of material 133 can also cause transducer wheel110 to bounce resulting in amplitude oscillations 181, 182, 183, 184 aswell. This is also due to fact prior art ultrasonic density detectionsystem 100 is heavy, i.e., lots of mass and inertia and, being an oldermechanical/pneumatic system with no feedback provision, prior artultrasonic density detection system 100 cannot react quickly oraccurately. While, these surface irregularity oscillations are not asproblematic as the initial bounce oscillations, they can still limit theaccuracy of prior art ultrasonic density detection system 100.

Another issue using prior art ultrasonic density detection system 100 isthat for various types of material making up sheet of material 133 thegoal constant pressure on transducer lever arm horizontal component 115of prior art traditional transducer lever arm 111 which, in turn,theoretically provides a constant pressure/force on transducer support113 of prior art traditional transducer lever arm 111 and transducerwheel 110, must be adjusted for the new material. Using prior artultrasonic density detection system 100 this adjustment is limited tochanging the pressure in prior art pneumatic position system air bag103. However, as discussed above, obtaining accurate pressure in priorart pneumatic position system air bag 103 is difficult and there are nofeedback controls for prior art pneumatic position system air bag 103.Consequently, this is highly problematic due to simple physics ofcompressibility of the prior art pneumatic position system air bag 103and for varying thicknesses of materials being analyzed.

In addition, the physical shape of lift wheel 141 is subjecteccentricity due to manufacturing imperfections and wear and tearresulting from the rebound force associated with the significant mass ofprior art ultrasonic density detection system 100. These factors alsocause a variation in applied force/pressure on transducer wheel 110 thatcannot be effectively identified, measured, or compensated for usingprior art ultrasonic density detection system 100.

In addition, as discussed above, prior art ultrasonic density detectionsystem 100 uses prior art transducer lever arm thickness/displacementsensor 123 to determine the thickness of the sheet of material, such assheet of material 133, by detecting/measuring the movement of prior arttransducer lever arm vertical thickness measurement component 119 when asheet of material, such as sheet of material 133, moves betweentransducer wheel 110 and lift wheel 141. This system is complicated,requires additional components and maintenance, adds mass in the form ofprior art transducer lever arm vertical thickness measurement component119, and is subject to failure of prior art transducer lever armthickness/displacement sensor 123.

In addition, as discussed above, prior art ultrasonic density detectionsystem 100 uses prior art sheet of material detector 135. This involvesyet more components that must be maintained and are subject to failure.In addition, prior art sheet of material detector 135 is subject tofalse indicators because prior art sheet of material detector 135 is apurely visual detector and therefore often mistakes debris on conveyorsystem 131 for a sheet of material, such as sheet of material 133. Thisalso complicates the operation of prior art ultrasonic density detectionsystem 100 and results in inefficient operation of prior art ultrasonicdensity detection system 100.

As discussed above, prior art ultrasonic density detection systems arelargely incapable of providing the consistent and accurate densityreadings now required in many industries. In addition, prior artultrasonic density detection systems have many parts and components thatare subject to failure, add unnecessary weight to the systems, requiresignificant maintenance, and are subject to failure. Consequently, priorart ultrasonic density detection systems are antiquated, largelyineffective, and are inefficient and expensive to operate.

What is needed is a technical solution to the technical problem ofproviding a method and system for determining the density of a sheet ofmaterial that accurately and consistently determines the density ofsheets of material in an effective and efficient manner and is capableof providing the density measurement accuracy now required in manyindustries.

SUMMARY

Embodiments of the present disclosure provide a technical solution tothe long-standing technical problem of providing a method and system fordetermining the density of a sheet of material that accurately andconsistently determines the density of sheets of material in aneffective and efficient manner and is capable of providing the densitymeasurement accuracy now needed in many industries.

To this end, the disclosed embodiments utilize a magnetic force feedbackactuator positioner to accurately maintain a constant selectedpressure/force between transducer elements and the surface of a sheet ofmaterial as the sheet of material moves through the position betweentransmitting transducer element and lift wheel, and/or receivertransducer element and lift wheel. Consequently, according to thedisclosed embodiments, the antiquated mechanical/pneumaticsprings/airbags of prior art ultrasonic density detection systems arereplaced with a highly responsive magnetic force feedback actuatorpositioner.

The disclosed use of a magnetic force feedback actuator positionerprovides not only for a method and system to maintain a precise andconstant force between the surface of a sheet of material and atransducer element, but it also provide reaction times that can allowfor adjustment to the introduction of a sheet of material into theposition between transducer element and lift wheel and/or variations inthe surface of a sheet of material, in nearly real time to all buteliminate the bounce/recovery oscillations associated with prior artultrasonic density detection systems. Consequently, the disclosedembodiments can obtain precise density measurements of an entire sheetof material without loss of data and with unprecedented accuracyunobtainable using prior art ultrasonic density detection systems.

In addition, in one embodiment, the magnetic force feedback actuatorpositioner can provide accurate displacement information for thicknessmeasurement superior to prior art ultrasonic density detection systemsby using current prior art transducer lever arm thickness/displacementsensors to detect the movement of prior art transducer lever armvertical thickness measurement components.

In addition, in one embodiment, the magnetic force feedback actuatorpositioner utilizes a displacement sensor to detect the presence of asheet of material to trigger the transmitting transducer element tobegin operation. This internal measurement ability of the magnetic forcefeedback actuator positioner can accurately and rapidly trigger pulsetransmission as a result of displacement without the use of mechanicalor electromechanical switches. Therefore, using the disclosedembodiments, the reliability and efficiency of operation is greatlyincreased compared to prior art ultrasonic density detection systemsthat can be falsely triggered by trash on the conveyor line.

By maintaining a precise constant pressure/force on transducer elements,and therefore keeping the pressure/force of the transducer elements onthe surface of sheet of material constant, the disclosed use of magneticforce feedback actuator positioner provides an accuracy and reliabilityof density measurements unobtainable using prior art ultrasonic densitydetection systems. This is accomplished by eliminating the relativelyantiquated mechanical/pneumatic prior art pneumatic position system airbag and spring systems. This, in turn eliminates the prior art PSI andgauge errors inherent in prior art ultrasonic density detection systemsand the resulting significant variance in density readings from actualdensity from pulse to pulse in the same sheet of material.

In addition, the disclosed use of magnetic force feedback actuatorpositioner provides for simple and precise force/pressure adjustmentsfor various types of material making up sheets of material. In addition,the disclosed use of magnetic force feedback actuator positionerprovides for the precise adjustment of applied pressure force tocompensate for lift wheel eccentricity due to manufacturingimperfections and wear and tear resulting from the rebound force.

In addition, the disclosed use of magnetic force feedback actuatorpositioner eliminates the need for prior art transducer lever armthickness/displacement sensors and prior art transducer lever armvertical thickness measurement components. This results in a simpler,lighter, and less failure prone system that require less maintenance

In addition, the disclosed use of magnetic force feedback actuatorpositioner eliminates the need for prior art sheet of material detector.This eliminates yet more components that need to be maintained, aresubject to failure, and are subject to false indicators using prior artultrasonic density detection systems.

As discussed in more detail below, the disclosed embodiments utilizing amagnetic force feedback actuator positioner are able to provide theprecise, consistent, and accurate density readings now needed/requiredin many industries. In addition, the disclosed embodiments utilizing amagnetic force feedback actuator positioner have fewer parts andcomponents than prior art ultrasonic density detection systems and aretherefore less subject to failure, are lighter, and require lessmaintenance Consequently, the disclosed embodiments utilizing a magneticforce feedback actuator positioner are more efficient and effective,than prior art ultrasonic density detection systems and are lessexpensive to operate.

As a result of these and other disclosed features, which are discussedin more detail below, the disclosed embodiments address the shortcomings of the prior art.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a photograph of a prior art ultrasonic density detectionsystem showing several key components.

FIG. 1B is a simplified block diagram of a side view of the prior artultrasonic density detection system of FIG. 1A showing several keycomponents before sheet of material, such as veneer, is fed into priorart ultrasonic density detection system.

FIG. 1C is a simplified block diagram of a side view of the prior artultrasonic density detection system of FIGS. 1A and 1B showing severalkey components as a sheet of material, such as veneer, passes throughprior art ultrasonic density detection system.

FIG. 1D is a simplified block diagram of a side view of the prior artultrasonic density detection system of FIGS. 1A, 1B AND 1C after a sheetof material, such as veneer, passes through prior art ultrasonic densitydetection system.

FIG. 1E is a line drawing of a prior art ultrasonic density detectionsystem 100 showing several key components in more detail.

FIG. 1F is a line drawing showing counter balance spring 105 of priorart ultrasonic density detection system 100 in more detail.

FIG. 1G is a line drawing showing prior art pneumatic position systemair bag 103 of prior art ultrasonic density detection system 100 in moredetail.

FIG. 1H is a line drawing of a transmitting transducer wheel/lift wheelreceiver transducer wheel/lift wheel pair of the prior art ultrasonicdensity detection system of FIGS. 1A through 1G showing more detailbefore a sheet of material, such as veneer, is fed into prior artultrasonic density detection system as is also depicted in FIGS. 1B and1D.

FIG. 1I is a line drawing of a transmitting transducer wheel/lift wheelreceiver transducer wheel/lift wheel pair of the prior art ultrasonicdensity detection system of FIGS. 1A through 1G showing more detailbefore or after a sheet of material, such as veneer, passes throughprior art ultrasonic density detection system as is also depicted inFIG. 1C.

FIG. 1J shows a representation of the bounce/recovery time problemassociated with prior art ultrasonic density detection systems.

FIG. 2A is a simplified block diagram of a side view of one illustrativeexample of the disclosed system for determining the density of a sheetof material showing several key components before sheet of material,such as veneer, is fed into the disclosed system for determining thedensity of a sheet of material in accordance with one embodiment.

FIG. 2B is a simplified block diagram of a side view of the oneillustrative example of the disclosed system for determining the densityof a sheet of material of FIG. 2A showing several key components as asheet of material, such as veneer, is passed through the disclosedsystem for determining the density of a sheet of material in accordancewith one embodiment.

FIG. 2C is a simplified block diagram of a side view of the oneillustrative example of the disclosed system for determining the densityof a sheet of material of FIGS. 2A and 2B showing several key componentsafter a sheet of material, such as veneer, exits the disclosed systemfor determining the density of a sheet of material in accordance withone embodiment.

FIG. 3A shows a cut away view of one illustrative example of a magneticforce feedback actuator positioner that can be used with oneillustrative example of the disclosed system for determining the densityof a sheet of material.

FIG. 3B shows one illustrative example of a currently available magneticforce feedback actuator positioner that can be used with oneillustrative example of the disclosed system for determining the densityof a sheet of material.

FIG. 3C shows another illustrative example of a currently availablemagnetic force feedback actuator positioner that can be used with oneillustrative example of the disclosed system for determining the densityof a sheet of material.

FIG. 3D shows an illustrative example of two currently availablemagnetic force feedback actuator positioners that can be used in tandemwith one illustrative example of the disclosed system for determiningthe density of a sheet of material.

FIG. 4 is a simplified flow chart representing one embodiment of thedisclosed method for determining the density of a sheet of material.

Common reference numerals are used throughout the figures and thedetailed description to indicate like elements. One skilled in the artwill readily recognize that the above figures are merely illustrativeexamples and that other architectures, modes of operation, orders ofoperation, and elements/functions can be provided and implementedwithout departing from the characteristics and features of theinvention, as set forth in the claims.

DETAILED DESCRIPTION

Embodiments will now be discussed with reference to the accompanyingfigures, which depict one or more exemplary embodiments. Embodiments maybe implemented in many different forms and should not be construed aslimited to the embodiments set forth herein, shown in the figures, ordescribed below. Rather, these exemplary embodiments are provided toallow a complete disclosure that conveys the principles of theinvention, as set forth in the claims, to those of skill in the art.

The disclosed embodiments utilize one or more magnetic force feedbackactuator positioners to accurately maintain a constant selectedpressure/force between transducer elements and the surface of a sheet ofmaterial as the sheet of material moves through the position between atransmitting transducer element and/or a receiver transducer element.Consequently, according to the disclosed embodiments, the antiquatedmechanical/pneumatic springs/airbags of prior art ultrasonic densitydetection systems are replaced with a highly responsive magnetic forcefeedback actuator positioner.

The disclosed use of a magnetic force feedback actuator positionerprovides not only for a method and system to maintain a precise andconstant force between the surface of a sheet of material and atransducer element, but it also provide reaction times that can allowfor adjustment to the introduction of a sheet of material into theposition between transducer element and a lift element, and/orvariations in the surface of a sheet of material, in nearly real time toall but eliminate the bounce/recovery oscillations associated with priorart ultrasonic density detection systems. Consequently, the disclosedembodiments can obtain precise density measurements of an entire sheetof material without loss of data and with unprecedented accuracyunobtainable using prior art ultrasonic density detection systems.

In addition, in one embodiment, the magnetic force feedback actuatorpositioner can provide accurate displacement information for thicknessmeasurement superior to prior art ultrasonic density detection systemsusing current prior art transducer lever arm thickness/displacementsensors to detect the movement of prior art transducer lever armvertical thickness measurement components.

In addition, in one embodiment, the magnetic force feedback actuatorpositioner utilizes a displacement sensor to detect the presence of asheet of material to trigger the transmitting transducer element tobegin operation. This internal measurement ability of the magnetic forcefeedback actuator positioner can accurately and rapidly trigger pulsetransmission as a result of displacement without the use of prior artswitching mechanisms. Therefore, using the disclosed embodiments, thereliability and efficiency of operation is greatly increased compared toprior art ultrasonic density detection systems that can be falselytriggered by trash on the conveyor line.

As discussed in more detail below, the disclosed embodiments utilizing amagnetic force feedback actuator positioner are able to provide theprecise, consistent, and accurate density readings now needed/requiredin many industries. In addition, the disclosed embodiments utilizing amagnetic force feedback actuator positioner have fewer parts andcomponents than prior art ultrasonic density detection systems and aretherefore less subject to failure, are lighter, and require lessmaintenance Consequently, the disclosed embodiments utilizing a magneticforce feedback actuator positioner are more efficient and effective,than prior art ultrasonic density detection systems and are lessexpensive to operate.

FIG. 2A is a simplified block diagram of a side view of one illustrativeexample of the disclosed system 200 for determining the density of asheet of material showing several key components before a sheet ofmaterial 133, such as veneer, is fed into the disclosed system 200 fordetermining the density of a sheet of material in accordance with oneembodiment.

FIG. 2B is a simplified block diagram of a side view of the oneillustrative example of the disclosed system 200 for determining thedensity of a sheet of material of FIG. 2A showing several key componentsas a sheet of material 133, such as veneer, is fed into and passesthrough the disclosed system 200 for determining the density of a sheetof material in accordance with one embodiment.

FIG. 2C is a simplified block diagram of a side view of the oneillustrative example of the disclosed system 200 for determining thedensity of a sheet of material of FIGS. 2A and 2B showing several keycomponents after a sheet of material 133, such as veneer, exits thedisclosed system 200 for determining the density of a sheet of materialin accordance with one embodiment.

As seen in FIGS. 2A through 2C, the disclosed system 200 for determiningthe density of a sheet of material includes: support frame 101; magneticforce feedback actuator positioner system 201 including magnetic forcefeedback actuator positioner 203 and magnetic force feedback actuatorpositioner control system 205; transducer wheel 110; magnetic forcefeedback actuator positioner controlled lever arm 211 includingtransducer element support 213, lever arm horizontal component 215, andlever arm pivot point 217; lever arm stop 221; conveyor system 131;sheet of material 133; lift wheel 141; and gaps 251 and 252 (FIG. 2B)between transducer wheel 110 and lift wheel 141.

Referring to FIGS. 2A through 2C and FIGS. 1A through 1G together andcomparing the disclosed system 200 for determining the density of asheet of material with prior art ultrasonic density detection system100, notably absent from the disclosed system 200 for determining thedensity of a sheet of material are: prior art pneumatic position systemair bag 103, prior art counter balance spring 105, prior art transducerlever arm vertical thickness measurement component 119, prior arttransducer lever arm thickness/displacement sensor 123, and prior artsheet of material detector 135. As discussed in more detail, not onlydoes the removal of these elements result in less elements, lessfailures, less maintenance, and less weight of the disclosed system 200for determining the density of a sheet of material compared to prior artultrasonic density detection system 100, but it also provides forsignificantly more accurate density measurements and simplicity ofoperation.

In one embodiment, support frame 101 is typically made up of severalbeam and frame components. Typically, these components are made ofstainless steel or a similarly solid, and heavy, material to providesupport and a framework for the disclosed system 200 for determining thedensity of a sheet of material.

As seen in FIGS. 2A through 2C, magnetic force feedback actuatorpositioner 203 of magnetic force feedback actuator positioner system 201is operatively coupled to prior art support frame 101 and lever armhorizontal component 215 of magnetic force feedback actuatorpositioner-controlled transducer lever arm 211.

Again, it is to be noted that, in one embodiment, prior art transducerlever arm vertical thickness measurement component 119 is not includedin magnetic force feedback actuator positioner-controlled transducerlever arm 211. This alone represents a manufacturing and weight savings.

As also seen in FIGS. 2A through 2C, magnetic force feedback actuatorpositioner system 201 includes magnetic force feedback actuatorpositioner control system 205 electrically coupled to magnetic forcefeedback actuator positioner 203 for transmitting and receiving signalsto and from magnetic force feedback actuator positioner 203 to controlmagnetic force feedback actuator positioner 203.

Again, referring to FIGS. 2A through 2C and FIGS. 1A through 1G togetherand comparing the disclosed system 200 for determining the density of asheet of material with prior art ultrasonic density detection system100, according to the disclosed embodiments, magnetic force feedbackactuator positioner system 201 replaces prior art pneumatic positionsystem air bag 103, prior art counter balance spring 105, prior arttransducer lever arm vertical thickness measurement component 119, priorart transducer lever arm thickness/displacement sensor 123, and priorart sheet of material detector 135.

As discussed in more detail below, the purpose of magnetic forcefeedback actuator positioner system 201 is to provide a very preciselycontrolled constant pressure on lever arm horizontal component 215 ofmagnetic force feedback actuator positioner-controlled transducer leverarm 211 which, in turn, provides a constant pressure on transducerelement support 213 of magnetic force feedback actuator positionercontrolled transducer lever arm 211 and transducer wheel 110.

As also discussed in more detail below, the disclosed use of magneticforce feedback actuator positioner system 201 mitigates and/oreliminates the numerous, and significant, limitations on the ability ofprior art ultrasonic density detection system 100 to accurately providethe theoretically constant pressure/force on transducer lever armhorizontal component and transducer wheel 110. Therefore, the discloseduse of magnetic force feedback actuator positioner system 201 providesfor density measurement accuracy unobtainable using prior art ultrasonicdensity detection systems, such as prior art ultrasonic densitydetection system 100.

As also seen in FIGS. 2A through 2C, magnetic force feedback actuatorpositioner-controlled transducer lever arm 211 is movably, i.e.,rotationally, operatively coupled to lever arm pivot point 217 such thatmagnetic force feedback actuator positioner-controlled transducer leverarm 211 can rotate/pivot in either direction 116 or 118 about lever armpivot point 217. As seen in FIGS. 2A through 2C, transducer wheel 110 issupported by transducer element support 213 of magnetic force feedbackactuator positioner controlled transducer lever arm 211 at rotatingcenter hub 112.

Of note, in the one illustrative example of one embodiment of FIGS. 2Athrough 2C, transducer wheel 110 is used as the housing enclosure of atransducer element, i.e., a transmitting or receiving transducerelement. However, transducer wheel 110 FIGS. 2A through 2C is merelyrepresentative of various types of transducer elements and/or transducerelement housings. In other embodiments, one or more of the transducerelements, i.e., a transmitting or receiving transducer elements, can beprovided with or without a housing and in some cases n a housing that isnot a transducer wheel. Consequently, the specific illustrative exampleof one embodiment of FIGS. 2A through 2C is not to be construed aslimiting the inventions as set forth in the claims.

Also seen in FIGS. 2A through 2C is lever arm stop 221. Lever arm stop221 prevents magnetic force feedback actuator positioner controlledtransducer lever arm 211 from pivoting too far in direction 116 suchthat transducer wheel 110 comes in contact with lift wheel 141 whenthere is no sheet of material 133 positioned between transducer wheel110 and lift wheel 141 (as shown in FIG. 2A). Consequently, lever armstop 221 ensures a minimal home gap 251 between transducer wheel 110 andlift wheel 141. Lever arm stop 221 is typically made of urethane or asimilar material.

FIGS. 2A through 2C also show sheet of material 133 being conveyed to,and passing through, the disclosed system 200 for determining thedensity of a sheet of material by conveyor system 131. In various cases,sheet of material 133 is a sheet of veneer, a sheet of any wood product,or a sheet of any material that is to be analyzed by the disclosedsystem 200 for determining the density of a sheet of material. Invarious cases, conveyor system 131 is any standard conveyor system suchas a traditional conveyor belt.

Referring to FIGS. 2A through 2C, in operation, sheet of material 133moves along conveyor system 131 to, and through, a density analysisstation including the disclosed system 200 for determining the densityof a sheet of material. As seen in FIG. 2A, in one embodiment, lever armstop 221 prevents magnetic force feedback actuator positioner-controlledtransducer lever arm 211 from pivoting too far in direction 116 suchthat transducer wheel 110 comes in contact with lift wheel 141 whenthere is no sheet of material 133 positioned between transducer wheel110 and lift wheel 141 (as shown in FIG. 2A).

Consequently, in one embodiment, lever arm stop 221 ensures a minimal,or equilibrium, home gap 251 between transducer wheel 110 and lift wheel141. In addition, in one embodiment, magnetic force feedback actuatorpositioner-controlled transducer lever arm 211 and transducer wheel 110are in the neutral home position at this time (FIGS. 2A and 2C).

Of note, the one illustrative example of one embodiment of FIGS. 2Athrough 2C includes lift wheel 141, and sheet of material 133 ispositioned between lift wheel 141 and a transducer element, i.e., atransmitting or receiving transducer element, such as represented bytransducer wheel 110. However, lift wheel 141 of FIGS. 2A through 2C ismerely representative of various mechanisms through which sheet ofmaterial passes such that sheet of material 133 is positioned betweenthese mechanisms and a transducer element, such as transducer wheel 110.In addition, in some embodiments, lift wheel 141 is not present, andsheet of material 133 is positioned between a flat surface and atransducer element, such as transducer wheel 110. Consequently, thespecific illustrative example of one embodiment of FIGS. 2A through 2Cis not to be construed as limiting the inventions as set forth in theclaims.

In one embodiment, magnetic force feedback actuator positioner 203 ofmagnetic force feedback actuator positioner system 201 maintains home,also known as a neutral or equilibrium, position as commanded bymagnetic force feedback actuator positioner control system 205 ofmagnetic force feedback actuator positioner system 201. In oneembodiment, the home position the gap 251 between the transducer wheel110 and the lift wheel 141 is approximately one tenth of an inch. Whilein this home position, actuator element 204 of magnetic force feedbackactuator positioner 203 can be commanded by magnetic force feedbackactuator positioner control system 205 of magnetic force feedbackactuator positioner system 201 to present only slight resistance torising as sheets of material 133 enter the gap 251/252 between thetransducer wheel 110 and the lift wheel 141. This fact, and the factmagnetic force feedback actuator positioner control system 205 ofmagnetic force feedback actuator positioner system 201 can reactextremely quickly to adjust the extension of actuator element 204 ofmagnetic force feedback actuator positioner 203 (on the order ofKilo-Hertz reaction time), means that the recovery/bounce oscillationissues associated with prior art systems is significantly mitigatedand/or virtually eliminated.

In one embodiment, then the lift of actuator element 204 of magneticforce feedback actuator positioner 203 is compressed by the entry ofsheet of material 133 into the gap 252 between the transducer wheel 110and the lift wheel 141 is detected, using magnetic force feedbackactuator positioner system 201, actuator element 204 of magnetic forcefeedback actuator positioner 203 of provides a very precisely controlledconstant pressure on lever arm horizontal component 215 of magneticforce feedback actuator positioner-controlled transducer lever arm 211which, in turn, provides a constant pressure on transducer elementsupport 213 of magnetic force feedback actuator positioner-controlledtransducer lever arm 211 and transducer wheel 110.

In one embodiment, once the sheet of material 133 passes through the gap252 between the transducer wheel 110 and the lift wheel 141, gap 252 isreduced back to the home gap 251 and the home command will be executedawaiting the next cycle.

Thus, using the disclosed magnetic force feedback actuator positioner,the far less precise and more complicated use of prior art transducerlever arm vertical thickness measurement component 119 and prior arttransducer lever arm thickness/displacement sensor 123 to make offsetthickness measurements is avoided.

Referring again to FIGS. 2A through 2C, as seen in FIG. 2B, as sheet ofmaterial 133 moves through the position between transducer wheel 110 andlift wheel 141, transducer wheel 110 is lifted up so that the gap 252between transducer wheel 110 and lift wheel 141 of FIG. 2B is greaterthat gap 251 of FIG. 2C, typically by a distance equal to the thicknessT of sheet of material 133. This, in turn, causes magnetic forcefeedback actuator positioner controlled transducer lever arm 211 topivot in direction 118 around lever arm pivot point 217 as transducerwheel 110 is lifted up.

In one embodiment, as sheet of material 133 moves between lift wheel 141and a transducer element, i.e., a transmitting or receiving transducerelement, such as represented by transducer wheel 110, actuator element204 of magnetic force feedback actuator positioner 203 is compressed(see FIG. 2B) by a precisely measurable distance equal to the thicknessof sheet of material 133. In one embodiment, magnetic force feedbackactuator positioner control system 205 then records this compressiondistance of actuator element 204 as the thickness T of sheet 133. Thus,using the disclosed magnetic force feedback actuator positioner, the farless precise and more complicated use of prior art transducer lever armvertical thickness measurement component 119 and prior art transducerlever arm thickness/displacement sensor 123 to make offset thicknessmeasurements is avoided.

In one embodiment, the disclosed system 200 for determining the densityof a sheet of material typically includes a minimum of two transducerwheels, and two lift wheels in pairs of transmitting transducer wheel110/lift wheel 141 and pairs of receiving transducer wheel 110/liftwheel 141. This is similar to the basic configuration shown in FIG. 1Awith magnetic force feedback actuator positioner system 201 replacingprior art pneumatic position systems 108. As the sheet of material 133is conveyed by the conveyor system 131 between the transmittingtransducer wheel 110 and lift wheel 141 and the receiving transducerwheel 110 and lift wheel 141 a first portion of the sheet of material133 is in contact with the transmitting transducer wheel 110 and liftwheel 141 at the same time a second portion of the sheet of material isin contact with the receiving transducer wheel 110 and lift wheel 141.As noted above, the transmitting transducer wheel 110 and lift wheel 141pair and the receiving transducer wheel 110 and lift wheel 141 aretypically separated by a precisely defined distance, often around sixfeet. However, the accurate measurement of the distance is moreimportant than the distance chosen.

In one embodiment, as sheet of material 133 moves between transmittinglift wheel 141 and a transducer element, i.e., a transmitting orreceiving transducer element, such as represented by transducer wheel110, actuator element 204 of magnetic force feedback actuator positioner203 is compressed (see FIG. 2B) by a precisely measurable distance equalto the thickness of sheet of material 133, typically 0.125-0.166 inchfor veneer. In one embodiment, magnetic force feedback actuatorpositioner control system 205 then records this compression distance ofactuator element 204 as the thickness T of sheet 133. In one embodiment,this compression distance of actuator element 204, and the thickness Tof sheet 133, is measure continuously via magnetic force feedbackactuator positioner control system 205 and an internal positionindication inside magnetic force feedback actuator positioner 203.

Once the first portion of the sheet of material 133 is between thetransmitting transducer wheel 110 and lift wheel 141 and, at the sametime, the second portion of the sheet of material 133 is between withthe receiving transducer wheel 110 and lift wheel 141, the transmittingtransducer element, i.e., in transducer wheel 110 or transducer wheel110 emits an ultrasonic signal (typically in pulses). By separating thetransmitting transducer wheel 110 and receiving transducer wheel 110, bythe precisely defined fixed distance, an ultrasonic pulse transmittedinto the first portion of the sheet of material 133 by the transmittingtransducer element, i.e., in transmitting transducer wheel 110, thentravels through the sheet of material and can be received by thereceiving transducer element, i.e., in the receiving transducer wheel110 at the second portion of the sheet of material 133 by passingthrough the sheet of material 133 between the transmitting transducerelement and the receiving transducer element.

As noted above, in the one illustrative example of one embodiment ofFIGS. 2A through 2C, transducer wheel 110 is used as the housingenclosure of a transducer element, i.e., a transmitting or receivingtransducer element. However, transducer wheel 110 FIGS. 2A through 2C ismerely representative of various types of transducer elements and/ortransducer element housings. In other embodiments, one or more of thetransducer elements, i.e., a transmitting or receiving transducerelements, can be provided with or without a housing and in some cases na housing that is not a transducer wheel. Consequently, the specificillustrative example of one embodiment of FIGS. 2A through 2C is not tobe construed as limiting the inventions as set forth in the claims.

Since the distance between the transmitting transducer element, i.e., ina transmitting transducer wheel 110, and receiving transducer element,i.e., in receiving transducer wheel 110 is known, the density of thesheet of material 133 can be determined by measuring the time it takesthe ultrasonic pulse to travel from the transmitting transducer element,i.e., transmitting transducer wheel 110, through the known distance inthe sheet of material 133, to the receiving transducer element, i.e.,receiving transducer wheel 110. The density of the sheet of material 133can then be determined based on the pulse travel time with shortertravel times generally indicating higher densities and longer traveltimes generally indicating lower densities. The correlation of pulsetravel time to density will vary from material to material making up thesheet of material 133.

As the sheet of material 133 moves through the disclosed system 200 fordetermining the density of a sheet of material and the position betweenthe transmitting transducer wheel 110/lift wheel 141, and the receivingtransducer wheel 110/lift wheel 141, multiple density readings arecaptured at multiple locations along the sheet of material 133. Adensity reading taken every one to six inches along the sheet ofmaterial 133 is common. However, this distance is typically determinedby the speed at which the sheet of material 133 is conveyed by conveyorsystem 131 or the time interval between transmitted pulse, or both, andtherefore can be any distance desired.

As also noted above, the one illustrative example of one embodiment ofFIGS. 2A through 2C includes lift wheel 141, and sheet of material 133is positioned between lift wheel 141 and a transducer element, i.e., atransmitting or receiving transducer element, such as represented bytransducer wheel 110. However, lift wheel 141 of FIGS. 2A through 2C ismerely representative of various mechanisms through which sheet ofmaterial passes such that sheet of material 133 is positioned betweenthese mechanisms and a transducer element, such as transducer wheel 110.In addition, in some embodiments, lift wheel 141 is not present, andsheet of material 133 is positioned between a flat surface and atransducer element, such as transducer wheel 110. Consequently, thespecific illustrative example of one embodiment of FIGS. 2A through 2Cis not to be construed as limiting the inventions as set forth in theclaims.

As also noted above, in the one illustrative example of one embodimentof FIGS. 2A through 2C, transducer wheel 110 is used as the housingenclosure of a transducer element, i.e., a transmitting or receivingtransducer element. However, transducer wheel 110 FIGS. 2A through 2C ismerely representative of various types of transducer elements and/ortransducer element housings. In other embodiments, one or more of thetransducer elements, i.e., a transmitting or receiving transducerelements, can be provided with or without a housing and in some cases na housing that is not a transducer wheel. Consequently, the specificillustrative example of one embodiment of FIGS. 2A through 2C is not tobe construed as limiting the inventions as set forth in the claims.

Once the density of the sheet of material 133 is known, this can be usedto determine a relative strength of the sheet of material 133, withhigher densities generally equating to higher strength and lowerdensities generally equating to lower strength. The correlation of thesheet of material density to the sheet of material strength will varyfrom material to material making up the sheet of material 133

Referring to FIG. 2C, once the sheet of material 133 passes through theposition between the transmitting transducer wheel 110 and lift wheel141, and the receiving transducer wheel 110 and lift wheel 141, thedisclosed system 200 for determining the density of a sheet of materialreturns to the starting/neutral positions of FIG. 2A. Consequently,lever arm stop 221 again prevents magnetic force feedback actuatorpositioner controlled transducer lever arm 211 from pivoting too far indirection 116 such that transducer wheel 110 comes in contact with liftwheel 141 when there is no sheet of material 133 positioned betweentransducer wheel 110 and lift wheel 141.

Consequently, lever arm stop 221 ensures a return to the minimal homegap 251 between transducer wheel 110 and lift wheel 141. In addition,magnetic force feedback actuator positioner-controlled transducer leverarm 211 and transducer wheel 110 are in the neutral/home position.

It is again important to note that the accuracy and reliability ofdensity measurements taken using the disclosed system 200 fordetermining the density of a sheet of material is almost entirelydependent on keeping a constant pressure on transducer wheel 110, andtherefore keeping the pressure/force of transducer wheel 110 on thesurface of sheet of material constant. Any variation in thispressure/force will result in less accurate density readings, withlarger variations resulting in larger inaccuracies. Using the disclosedsystem 200 for determining the density of a sheet of material this isaccomplished using state of the art electronics in the form of magneticforce feedback actuator positioner system 201, including and magneticforce feedback actuator positioner 203 and magnetic force feedbackactuator positioner control system 205.

As noted above, the purpose magnetic force feedback actuator positionersystem 201 is to provide a very precisely controlled constant pressureon lever arm horizontal component 215 of magnetic force feedbackactuator positioner-controlled transducer lever arm 211 which, in turn,provides a constant pressure on transducer element support 213 ofmagnetic force feedback actuator positioner-controlled transducer leverarm 211 and transducer wheel 110.

As also noted above, the disclosed use of magnetic force feedbackactuator positioner system 201 mitigates and/or eliminates the numerous,and significant, limitations on the ability of prior art ultrasonicdensity detection system 100 to accurately provide the theoreticallyconstant pressure/force on transducer lever arm horizontal component andtransducer wheel 110. Therefore, the disclosed use of magnetic forcefeedback actuator positioner system 201 provides for density measurementaccuracy unobtainable using prior art ultrasonic density detectionsystems, such as prior art ultrasonic density detection system 100.

In various embodiments, magnetic force feedback actuator positionersystem 201 and magnetic force feedback actuator positioner 203 can beany of several magnetic force feedback actuator positioners and systemsknown in the art, and that are commercially available from severalmanufactures.

In other embodiments, magnetic force feedback actuator positioner system201 and magnetic force feedback actuator positioner 203 can be anymagnetic force feedback actuator positioner or system as discussedherein, known/available at the time of filing, and/or a developed/madeavailable after the time of filing capable of providing and maintaininga very precisely controlled constant pressure on lever arm horizontalcomponent 215 of magnetic force feedback actuator positioner-controlledtransducer lever arm 211 which, in turn, provides a constant pressure ontransducer element support 213 of magnetic force feedback actuatorpositioner-controlled transducer lever arm 211 and transducer wheel 110.

FIG. 3A shows a cut away view of one illustrative example of a onemagnetic force feedback actuator positioner 203 that can be used withone illustrative example of the disclosed system 200 for determining thedensity of a sheet of material. Referring to FIGS. 2A through 2C andFIG. 3A, as seen in FIG. 3A, magnetic force feedback actuator positioner203 includes actuator element 204, actuator element end 206, andactuator housing 303.

FIG. 3B shows one illustrative example of a currently available magneticforce feedback actuator positioner 203 that can be used with oneillustrative example of the disclosed system 200 for determining thedensity of a sheet of material. Referring to FIGS. 2A through 2C andFIG. 3B, as seen in FIG. 3B, magnetic force feedback actuator positioner203 includes actuator element 204, actuator element end 206, actuatorhousing 303, control input module 325 for receiving and sending signalsto magnetic force feedback actuator positioner control system 205, andcontrol wires 327 for transmitting signals between force feedbackactuator positioner control system 202 and magnetic force feedbackactuator positioner 203.

FIG. 3C shows one illustrative example of a currently available magneticforce feedback actuator positioner 203 that can be used with oneillustrative example of the disclosed system 200 for determining thedensity of a sheet of material. Referring to FIGS. 2A through 2C andFIG. 3C, as seen in FIG. 3C, magnetic force feedback actuator positioner203 includes actuator element 204, actuator element end 206, actuatorhousing 303, control input module 325 for receiving and sending signalsto magnetic force feedback actuator positioner control system 205, andcontrol wires 327 for between force feedback actuator positioner controlsystem 202 and magnetic force feedback actuator positioner 203.

FIG. 3D shows one illustrative example of two currently availablemagnetic force feedback actuator positioners 203 that can be used withone illustrative example of the disclosed system 200 for determining thedensity of a sheet of material. Referring to FIGS. 2A through 2C andFIG. 3D, as seen in FIG. 3D, each of magnetic force feedback actuatorpositioners 203 includes actuator element 204, actuator element end 206,actuator housing 303, control input module 325 for receiving and sendingsignals to magnetic force feedback actuator positioner control system205, and control wires 327 for transmitting signals between magneticforce feedback actuator positioner between force feedback actuatorpositioner control system 205 and magnetic force feedback actuatorpositioner 203.

In some embodiments a magnetic force feedback actuator positioner system201 includes a magnetic force feedback actuator positioner 203 that usesgenerated magnetic fields produced by electromagnetic coils in themagnetic force feedback actuator positioner housing 303 to impartLorentz force onto permanent magnets contained within actuator element204. This, in turn causes actuator element 204 to move linearly in andout of magnetic force feedback actuator positioner housing 303 and toapply a desired selected force at actuator element end 206. Thisparticular design contains just a single moving part, i.e., actuatorelement 204. Therefore, failure and maintenance problems aresignificantly reduced.

In addition, in some embodiments, magnetic force feedback actuatorpositioner system 201 and magnetic force feedback actuator positioner203 operate in a forced feedback loop control mode whereby the magneticforce feedback actuator positioner system 201 includes a magnetic forcefeedback actuator positioner 203 that senses force output at actuatorelement end 206 and thus can feel detect/identify when a force or forcechange is imparted onto actuator element end 206. In some embodiments,this forced feedback loop control can react to a change in force in lessthan one millisecond. This allows magnetic force feedback actuatorpositioner system 201 and magnetic force feedback actuator positioner203 to respond to changes in forces, or other inputs, nearlyinstantaneously. In addition, the inherent low friction contactlesscharacteristics of magnetic force feedback actuator positioner 203permit the resolution of that response to be on the scale of milligrams.This allows magnetic force feedback actuator positioner system 201 andmagnetic force feedback actuator positioner 203 to be commanded bymagnetic force feedback actuator positioner control system 205 to exerta very specific and precise level of force directly to lever armhorizontal component 215 of magnetic force feedback actuatorpositioner-controlled transducer lever arm 211 which, in turn, providesa constant pressure on transducer element support 213 of magnetic forcefeedback actuator positioner-controlled transducer lever arm 211 andtransducer wheel 110 and adjust the applied force to changes in sheet ofmaterial surface/thickness, wheel eccentricities, and the introductionof a sheet of material almost instantaneously and without therecovery/bounce issues of prior at systems.

As noted above, in various embodiments, magnetic force feedback actuatorpositioner system 201 and magnetic force feedback actuator positioner203 can be any of several magnetic force feedback actuator positionersand systems known in the art and that are commercially available fromseveral manufactures. Consequently, the structure and operation ofmagnetic force feedback actuator positioner systems and magnetic forcefeedback actuator positioners is known. Therefore, a more detaileddiscussion of any specific magnetic force feedback actuator positionersand systems is omitted here to avoid detracting from the generaldescription of the disclosed embodiments.

The disclosed use of magnetic force feedback actuator positioner system201 and magnetic force feedback actuator positioner 203 provides notonly for a method and system to maintain a precise and constant forcebetween the surface of a sheet of material and a transducer element, butit also provide reaction times that can allow for adjustment to theintroduction of a sheet of material into the position between transducerelement and a lift element, and/or variations in the surface of a sheetof material, in nearly real time to all but eliminate thebounce/recovery oscillations associated with prior art ultrasonicdensity detection systems. Consequently, the disclosed embodiments canobtain precise density measurements of an entire sheet of materialwithout loss of data and with unprecedented accuracy unobtainable usingprior art ultrasonic density detection systems.

In addition, in one embodiment, magnetic force feedback actuatorpositioner system 201 and magnetic force feedback actuator positioner203 can provide accurate displacement information for thicknessmeasurement superior to prior art ultrasonic density detection systemsby using current prior art transducer lever arm thickness/displacementsensors to detect the movement of prior art transducer lever armvertical thickness measurement components.

In addition, in one embodiment, magnetic force feedback actuatorpositioner system 201 and magnetic force feedback actuator positioner203 utilizes an integral displacement system to detect the presence of asheet of material to trigger the transmitting transducer element tobegin operation. This internal measurement ability of the magnetic forcefeedback actuator positioner can accurately and rapidly trigger pulsetransmission as a result of displacement without using prior artswitching mechanisms. Therefore, using the disclosed embodiments, thereliability and efficiency of operation is greatly increased compared toprior art ultrasonic density detection systems that can be falselytriggered by trash on the conveyor line.

As discussed in more detail below, the disclosed embodiments utilizingmagnetic force feedback actuator positioner system 201 and magneticforce feedback actuator positioner 203 are able to provide the precise,consistent, and accurate density readings now needed/required in manyindustries. In addition, the disclosed embodiments utilizing magneticforce feedback actuator positioner system 201 and magnetic forcefeedback actuator positioner 203 have fewer parts and components thanprior art ultrasonic density detection systems and are therefore lesssubject to failure, are lighter, and require less maintenanceConsequently, the disclosed embodiments utilizing magnetic forcefeedback actuator positioner system 201 and magnetic force feedbackactuator positioner 203 are more efficient and effective, than prior artultrasonic density detection systems and are less expensive to operate.

FIG. 4 is a simplified flow chart representing one embodiment of thedisclosed method 400 for determining the density of a sheet of material.

As seen in FIG. 4 , in one embodiment, the disclosed method 400 fordetermining the density of a sheet of material begins 401 and processflow proceeds to 403.

In one embodiment, at 403 at least one transmitting transducer elementis provided. In one embodiment, the at least one transmitting transducerelement is contained in a provided transmitting transducer elementwheel.

In one embodiment, once at least one transmitting transducer element isprovided at 403, process flow proceeds to 405. In one embodiment, at 405at least one receiving transducer element is provided. In oneembodiment, the at least one receiving transducer element is containedin a provided receiving transducer element wheel.

In one embodiment, the receiving transducer element is positioned adefined distance from the transmitting transducer element for receivingthe ultrasonic signals from the transmitting transducer element.

In one embodiment, once at least one receiving transducer element isprovided at 405, process flow proceeds to 407. In one embodiment, at 407a conveyor system is provided to convey a sheet of material to thetransmitting transducer element and the receiving transducer element.

In one embodiment, once a conveyor system is provided to convey a sheetof material to the transmitting transducer element and the receivingtransducer element at 407, process flow proceeds to 409. In oneembodiment, at 409 at least one transmitting transducer lift element isprovided and positioned such that a sheet of material passes between thetransmitting transducer element and the transmitting transducer liftelement as the conveyor system conveys the sheet of material past thetransmitting transducer element and the receiving transducer element. Inone embodiment, the at least one transmitting transducer lift element istransmitting transducer lift wheel.

In one embodiment, once at least one transmitting transducer liftelement is provided at 409, process flow proceeds to 411. In oneembodiment, at 411 at least one receiving transducer lift element isprovided and positioned such that a sheet of material passes between thereceiving transducer element and the transmitting transducer liftelement as the conveyor system conveys the sheet of material past thetransmitting transducer element and the receiving transducer element.

In one embodiment, once at least one receiving transducer lift wheel isprovided at 411, process flow proceeds to 413. In one embodiment, at 413at least one magnetic force feedback actuator positioner is provided andoperationally coupled to the transmitting transducer element to apply aselected constant force on the transmitting transducer element andmaintain a constant pressure of the transmitting transducer element onthe first portion of the surface of a sheet of material as the sheet ofmaterial is conveyed by the conveyor system past the transmittingtransducer element and the receiving transducer element. In oneembodiment, the at least one receiving transducer lift element isreceiving transducer lift wheel.

In one embodiment, once at least one magnetic force feedback actuatorpositioner is provided and operationally coupled to the transmittingtransducer element at 413, process flow proceeds to 415. In oneembodiment, at 415 at least one magnetic force feedback actuatorpositioner is provided and operationally coupled to the receivingtransducer element to apply a selected constant force on the receivingtransducer element and maintain a constant pressure of the receivingtransducer element on the second portion of the surface of a sheet ofmaterial as the sheet of material is conveyed by the conveyor systempast the transmitting transducer wheel and the receiving transducerelement.

Of note, in one embodiment, the at least one magnetic force feedbackactuator positioner of 413 and the at least one magnetic force feedbackactuator positioner of 413 can a single magnetic force feedback actuatorpositioner. In other embodiments, the at least one magnetic forcefeedback actuator positioner of 413 and the at least one magnetic forcefeedback actuator positioner of 413 can be separate magnetic forcefeedback actuator positioners. In some embodiments, the at least onemagnetic force feedback actuator positioner of 413 and the at least onemagnetic force feedback actuator positioner of 413 are controlled byseparate control systems. In other embodiments, the at least onemagnetic force feedback actuator positioner of 413 and the at least onemagnetic force feedback actuator positioner of 413 are controlled intandem by one or more control systems.

In one embodiment, once at least one magnetic force feedback actuatorpositioner is provided and operationally coupled to the receivingtransducer element at 415 process flow proceeds to 417. In oneembodiment, at 417 a sheet of material is positioned on the conveyorsystem of 407.

In one embodiment, the sheet of material is a sheet of wood product. Inone embodiment, the sheet of material is a sheet of veneer.

In one embodiment, once the sheet of material is positioned on theconveyor system of at 417, process flow proceeds to 419. In oneembodiment, at 419 the conveyor system conveys the sheet of materialpast the transmitting transducer element and the receiving transducerelement. In one embodiment, as the conveyor system conveys the sheet ofmaterial past the transmitting transducer element and the receivingtransducer element, a first portion of a surface of the sheet ofmaterial is positioned between the transmitting transducer element andthe transmitting transducer lift element and, simultaneously, a secondportion of a surface of the sheet of material is positioned between thereceiving transducer element and receiving transducer lift element.

In one embodiment, as the conveyor system conveys the sheet of materialpast the transmitting transducer element and the receiving transducerelement, the at least one magnetic force feedback actuator positionercoupled to the transmitting transducer element applies and maintains theselected constant force on the transmitting transducer element andmaintains a constant pressure of the transmitting transducer element onthe first portion of the surface of a sheet of material.

In addition, as the conveyor system conveys the sheet of material pastthe transmitting transducer element and the receiving transducerelement, the at least one magnetic force feedback actuator positionercoupled to the receiving transducer element applies and maintains theselected constant force on the receiving transducer element andmaintains a constant pressure of the receiving transducer element on thesecond portion of the surface of a sheet of material.

As noted above, in one embodiment, the at least one magnetic forcefeedback actuator positioner of 413 and the at least one magnetic forcefeedback actuator positioner of 413 can a single magnetic force feedbackactuator positioner. In other embodiments, the at least one magneticforce feedback actuator positioner of 413 and the at least one magneticforce feedback actuator positioner of 413 can be separate magnetic forcefeedback actuator positioners. In some embodiments, the at least onemagnetic force feedback actuator positioner of 413 and the at least onemagnetic force feedback actuator positioner of 413 are controlled byseparate control systems. In other embodiments, the at least onemagnetic force feedback actuator positioner of 413 and the at least onemagnetic force feedback actuator positioner of 413 are controlled intandem by a common control system.

In one embodiment, once the conveyor system conveys the sheet ofmaterial past the transmitting transducer element and the receivingtransducer element at 419, process flow proceeds to 421. In oneembodiment, at 421 density data for the sheet of material is obtained.

In one embodiment, at 421, as the conveyor system conveys the sheet ofmaterial past the transmitting transducer element and the receivingtransducer element, ultrasonic signals are generated and transmittedfrom the transmitting transducer element. The ultrasonic signals enterthe sheet of material at the first portion of the surface of the sheetof material and passes through the sheet of material to be received bythe receiving transducer element at the second portion of the surface ofthe sheet of material.

In one embodiment, based on a time the ultrasonic signals take to movefrom the transmitting transducer element at first portion of the surfaceof the sheet of material, pass through the sheet of material, and thenbe received by the receiving transducer element at the second portion ofthe surface of the sheet of material, density data for the sheet ofmaterial can be determined.

In one embodiment, once density data for the sheet of material isobtained at 421, process flow proceeds to 423. In one embodiment, at 423the strength of the sheet of material is determined and/or a gradeassigned to the sheet of material that is used to determine how thesheet of material can be used.

In one embodiment, at 423 the density data obtained using the disclosedmethod for determining the density of a sheet of material at 421 is usedto determine the strength of the sheet of material. In one embodiment,density data obtained using the disclosed method for determining thedensity of a sheet of material is used, at least in part, to determine agrade assigned to the sheet of material. In one embodiment, the gradeassigned to the sheet of material is used to determine how the sheet ofmaterial is used.

In one embodiment, once the strength of the sheet of material isdetermined and/or a grade assigned to the sheet of material that is usedto determine how the sheet of material can be used at 423, process flowproceeds to 430. In one embodiment, at 430, method 400 is exited toawait the introduction of the next sheet of material.

As discussed above, the disclosed embodiments utilize one or moremagnetic force feedback actuator positioners to accurately maintain aconstant selected pressure/force between transducer elements and thesurface of a sheet of material as the sheet of material moves throughthe position between a transmitting transducer element and/or a receivertransducer element. Consequently, according to the disclosedembodiments, the antiquated mechanical/pneumatic springs/airbags ofprior art ultrasonic density detection systems are replaced with ahighly responsive magnetic force feedback actuator positioner.

The disclosed use of a magnetic force feedback actuator positionerprovides not only for a method and system to maintain a precise andconstant force between the surface of a sheet of material and atransducer element, but it also provides reaction times that can allowfor adjustment to the introduction of a sheet of material into theposition between transducer element and a lift element, and/orvariations in the surface of a sheet of material, in nearly real time toall but eliminate the bounce/recovery oscillations associated with priorart ultrasonic density detection systems. Consequently, the disclosedembodiments can obtain precise density measurements of an entire sheetof material without loss of data and with unprecedented accuracyunobtainable using prior art ultrasonic density detection systems.

In addition, in one embodiment, the magnetic force feedback actuatorpositioner can provide accurate displacement information for thicknessmeasurement superior to prior art ultrasonic density detection systemsby using current prior art transducer lever arm thickness/displacementsensors to detect the movement of prior art transducer lever armvertical thickness measurement components.

In addition, in one embodiment, the magnetic force feedback actuatorpositioner utilizes an internal displacement/photo switch to detect thepresence of a sheet of material to trigger the transmitting transducerwheel to begin operation. This internal measurement ability of themagnetic force feedback actuator positioner can accurately and rapidlytrigger pulse transmission as a result of displacement. Therefore, usingthe disclosed embodiments, the reliability and efficiency of operationis greatly increased compared to prior art ultrasonic density detectionsystems that can be falsely triggered by trash on the conveyor line.

By maintaining a precise constant pressure/force on transducer wheels,and therefore keeping the pressure/force of the transducer wheels on thesurface of sheet of material constant, the disclosed use of magneticforce feedback actuator positioner provides an accuracy and reliabilityof density measurements unobtainable using prior art ultrasonic densitydetection systems. This is accomplished by eliminating the relativelyantiquated mechanical/pneumatic prior art pneumatic position system airbag and spring systems. This, in turn eliminates the prior art PSI andgauge errors inherent in prior art ultrasonic density detection systemsand the resulting significant variance in density readings from actualdensity from pulse to pulse in the same sheet of material.

In addition, the disclosed use of magnetic force feedback actuatorpositioner provides for simple and precise force/pressure adjustmentsfor various types of material making up sheets of material. In addition,the disclosed use of magnetic force feedback actuator positionerprovides for the precise adjustment of applied pressure/force tocompensate for lift wheel eccentricity due to manufacturingimperfections and wear and tear resulting from the rebound force.

In addition, the disclosed use of magnetic force feedback actuatorpositioner eliminates the need for prior art transducer lever armthickness/displacement sensors and prior art transducer lever armvertical thickness measurement components. This results in a simpler,lighter, and less failure prone system that require less maintenance.

In addition, the disclosed use of magnetic force feedback actuatorpositioner eliminates the need for prior art sheet of material detector.This eliminates yet more components that need to be maintained, aresubject to failure, and are subject to false indicators using prior artultrasonic density detection systems.

Consequently, the disclosed embodiments utilizing a magnetic forcefeedback actuator positioner are able to provide the precise,consistent, and accurate density readings now needed/required in manyindustries. In addition, the disclosed embodiments utilizing a magneticforce feedback actuator positioner have fewer parts and components thanprior art ultrasonic density detection systems and are therefore lesssubject to failure, are lighter, and require less maintenanceConsequently, the disclosed embodiments utilizing a magnetic forcefeedback actuator positioner are more efficient and effective, thanprior art ultrasonic density detection systems and are less expensive tooperate.

In one embodiment, a system for determining the density of a sheet ofmaterial is disclosed that includes a density analysis station. In oneembodiment, the density analysis station includes at least onetransmitting transducer element for generating and transmittingultrasonic signals.

In one embodiment, the density analysis station also includes at leastone receiving transducer element positioned a defined/known distancefrom the transmitting transducer element for receiving the ultrasonicsignals from the transmitting transducer element.

In one embodiment, a conveyor system is used to convey a sheet ofmaterial through the density analysis station. In one embodiment, as theconveyor system conveys the sheet of material through the densityanalysis station the transmitting transducer element is in contact witha first portion of a surface of the sheet of material and the receivingtransducer element is in contact with a second portion of the surface ofthe sheet of material at the defined/known distance from the firstportion of the surface of the sheet of material.

In one embodiment, ultrasonic signals are generated and transmitted fromthe transmitting transducer element into the sheet of material at thefirst portion of the surface of the sheet of material and pass throughthe sheet of material to be received by the receiving transducer elementat the second portion of the surface of the sheet of material.

In one embodiment, at least one magnetic force feedback actuatorpositioner is operationally coupled to the transmitting transducerelement. In one embodiment, the at least one magnetic force feedbackactuator positioner is used to apply and maintain a selected constantforce on the transmitting transducer element to maintain a constantpressure of transmitting transducer element on the first portion of thesurface of the sheet of material as the sheet of material is conveyed bythe conveyor system through the density analysis station.

In one embodiment, a transmitting transducer element lever arm isoperationally coupled to the at least one magnetic force feedbackactuator positioner. In one embodiment, the transmitting transducerelement lever arm is also operationally coupled to the transmittingtransducer element. In this way the at least one magnetic force feedbackactuator positioner applies and maintains a selected force on thetransmitting transducer element through the transmitting transducerelement lever arm to keep a selected pressure between the transmittingtransducer element and the first portion of the surface of the sheet ofmaterial.

In one embodiment, at least one magnetic force feedback actuatorpositioner is operationally coupled to the receiving transducer elementto apply and maintain a selected constant force on the receivingtransducer element. In this way a constant pressure of the receivingtransducer element on the second portion of the surface of the sheet ofmaterial is maintained as the sheet of material is conveyed by theconveyor system through the density analysis station.

In one embodiment, the at least one magnetic force feedback actuatorpositioner operationally coupled to the transmitting transducer elementand the at least one magnetic force feedback actuator positioneroperationally coupled to the receiving transducer element are controlledto operate in tandem by a common magnetic force feedback actuatorpositioner control system.

In one embodiment, a receiving transducer element lever arm isoperationally coupled to at least one magnetic force feedback actuatorpositioner and the receiving transducer element lever arm is alsooperationally coupled to the receiving transducer element. In this waythe at least one magnetic force feedback actuator positioner applies andmaintains a selected force on the receiving transducer element throughthe receiving transducer element lever arm to keep a selected pressurebetween the receiving transducer element and the second portion of thesurface of the sheet of material.

In one embodiment, the transmitting transducer element for generatingand transmitting ultrasonic signals is contained in a transmittingtransducer wheel and as the conveyor system conveys the sheet ofmaterial through the density analysis station the transmittingtransducer wheel is in contact with a first portion of a surface of thesheet of material and the receiving transducer element is in contactwith a second portion of the surface of the sheet of material at thedefined/known distance from the first portion of the surface of thesheet of material. In one embodiment, ultrasonic signals generated andtransmitted from the transmitting transducer element in the transmittingtransducer wheel enter the sheet of material at the first portion of thesurface of the sheet of material and pass through the sheet of materialto be received by the receiving transducer element at the second portionof the surface of the sheet of material.

In one embodiment, the sheet of material is a sheet of wood product. Inone embodiment, the sheet of material is a sheet of veneer.

In one embodiment, density data obtained using the disclosed system fordetermining the density of a sheet of material is used to determine thestrength of the sheet of material. In one embodiment, density dataobtained using the disclosed system for determining the density of asheet of material is used, at least in part, to determine a gradeassigned to the sheet of material. In one embodiment, the grade assignedto the sheet of material is used to determine how the sheet of materialis used.

In one embodiment, a system for determining the density of a sheet ofmaterial is disclosed that includes at least one transmitting transducerwheel. In one embodiment, the transmitting transducer wheel includes atransmitting transducer element for generating and transmittingultrasonic signals.

In one embodiment, the disclosed system for determining the density of asheet of material includes at least one receiving transducer element. Inone embodiment, the receiving transducer element is positioned adefined/known distance from the transmitting transducer wheel forreceiving the ultrasonic signals from the transmitting transducerelement in the transmitting transducer wheel.

In one embodiment, a conveyor system is used to convey a sheet ofmaterial to the transmitting transducer wheel and the receivingtransducer element. In one embodiment, as the conveyor system conveysthe sheet of material to the transmitting transducer wheel and thereceiving transducer element, the transmitting transducer wheel is incontact with a first portion of a surface of the sheet of material andthe receiving transducer element is in contact with a second portion ofthe surface of the sheet of material at the same time at thedefined/known distance from the first portion of the surface of thesheet of material.

In one embodiment, the ultrasonic signals generated and transmitted fromthe transmitting transducer element of the transmitting transducer wheelenter the sheet of material at the first portion of the surface of thesheet of material and pass through the sheet of material to be receivedby the receiving transducer element at the second portion of the surfaceof the sheet of material.

In one embodiment, at least one magnetic force feedback actuatorpositioner is operationally coupled to the transmitting transducer wheelto apply a selected constant force on the transmitting transducer wheeland maintain a constant pressure of the transmitting transducer wheel onthe first portion of the surface of the sheet of material as the sheetof material is conveyed by the conveyor system through the densityanalysis station.

In one embodiment, at least one magnetic force feedback actuatorpositioner is operationally coupled to the receiving transducer elementto apply a selected constant force on the receiving transducer elementand maintain a constant pressure of the receiving transducer element onthe second portion of the surface of the sheet of material as the sheetof material is conveyed by the conveyor system through the densityanalysis station.

In one embodiment, a transmitting transducer element lever arm isoperationally coupled to the at least one magnetic force feedbackactuator positioner and the transmitting transducer wheel. In this waythe at least one magnetic force feedback actuator positioner is used toapply a selected force on the transmitting transducer wheel through thetransmitting transducer element lever arm to keep a selected pressurebetween the transmitting transducer wheel and the first portion of thesurface of the sheet of material.

In one embodiment, a receiving transducer element lever arm isoperationally coupled to the at least one magnetic force feedbackactuator positioner and the receiving transducer element. In this way,the at least one magnetic force feedback actuator positioner is used toapply a selected force on the receiving transducer element through thereceiving transducer element lever arm to keep a selected pressurebetween the receiving transducer element and the second portion of thesurface of the sheet of material.

In one embodiment, the sheet of material is a sheet of wood product. Inone embodiment, the sheet of material is a sheet of veneer.

In one embodiment, density data obtained using the disclosed system fordetermining the density of a sheet of material is used to determine thestrength of the sheet of material. In one embodiment, density dataobtained using the disclosed system for determining the density of asheet of material is used, at least in part, to determine a gradeassigned to the sheet of material. In one embodiment, the grade assignedto the sheet of material is used to determine how the sheet of materialis used.

In one embodiment, a system for determining the density of a sheet ofmaterial is disclosed that includes at least one transmitting transducerwheel. In one embodiment, the transmitting transducer wheel includes atransmitting transducer element for generating and transmittingultrasonic signals.

In one embodiment, the disclosed system for determining the density of asheet of material includes at least one receiving transducer element,the receiving transducer element is positioned a defined/known distancefrom the transmitting transducer wheel for receiving the ultrasonicsignals from the transmitting transducer element in the transmittingtransducer wheel.

In one embodiment, a conveyor system is used to convey a sheet ofmaterial to the transmitting transducer wheel and the receivingtransducer element. In one embodiment, as the conveyor system conveysthe sheet of material to the transmitting transducer wheel and thereceiving transducer element, the transmitting transducer wheel is incontact with a first portion of a surface of the sheet of material andthe receiving transducer element is in contact with a second portion ofthe surface of the sheet of material at the same time at thedefined/known distance from the first portion of the surface of thesheet of material.

In one embodiment, the ultrasonic signals generated and transmitted fromthe transmitting transducer element of the transmitting transducer wheelenter the sheet of material at the first portion of the surface of thesheet of material and pass through the sheet of material to be receivedby the receiving transducer element at the second portion of the surfaceof the sheet of material.

In one embodiment, at least one transmitting transducer lift wheel ispositioned such that the sheet of material passes between thetransmitting transducer wheel and the transmitting transducer lift wheelas the conveyor system conveys the sheet of material past thetransmitting transducer wheel and the receiving transducer element.

In one embodiment, at least one magnetic force feedback actuatorpositioner is operationally coupled to the transmitting transducer wheelto apply a selected constant force on the transmitting transducer wheeland maintain a constant pressure of the transmitting transducer wheel onthe first portion of the surface of the sheet of material as the sheetof material is conveyed by the conveyor system past the transmittingtransducer wheel and the receiving transducer element.

In one embodiment, at least one magnetic force feedback actuatorpositioner is operationally coupled to the receiving transducer elementto apply a selected constant force on the receiving transducer elementto maintain a constant pressure of the receiving transducer element onthe second portion of the surface of the sheet of material as the sheetof material is conveyed by the conveyor system through the past thetransmitting transducer wheel and the receiving transducer element.

In one embodiment, the receiving transducer element for receiving theultrasonic signals is contained in a receiving transducer wheel.

In one embodiment, at least one receiving transducer lift wheel ispositioned such that the sheet of material passes between the receivingtransducer wheel and the receiving transducer lift wheel as the conveyorsystem conveys the sheet of material to the transmitting transducerwheel and the receiving transducer wheel.

In one embodiment, a transmitting transducer element lever arm isoperationally coupled to the at least one magnetic force feedbackactuator positioner and the transmitting transducer wheel. In this waythe at least one magnetic force feedback actuator positioner is used toapply a selected force on the transmitting transducer wheel through thetransmitting transducer element lever arm to keep a selected pressurebetween the transmitting transducer wheel and the first portion of thesurface of the sheet of material.

In one embodiment, a receiving transducer element lever arm isoperationally coupled to the at least one magnetic force feedbackactuator positioner and the receiving transducer wheel. In this way, theat least one magnetic force feedback actuator positioner is used toapply a selected force on the receiving transducer wheel through thereceiving transducer element lever arm to keep a selected pressurebetween the receiving transducer wheel and the second portion of thesurface of the sheet of material.

In one embodiment, the sheet of material is a sheet of wood product. Inone embodiment, the sheet of material is a sheet of veneer.

In one embodiment, density data obtained using the disclosed system fordetermining the density of a sheet of material is used to determine thestrength of the sheet of material. In one embodiment, density dataobtained using the disclosed system for determining the density of asheet of material is used, at least in part, to determine a gradeassigned to the sheet of material. In one embodiment, the grade assignedto the sheet of material is used to determine how the sheet of materialis used.

In one embodiment, a method for determining the density of a sheet ofmaterial is disclosed that includes providing a density analysisstation. In one embodiment, the density analysis station includes atleast one transmitting transducer element for generating andtransmitting ultrasonic signals.

In one embodiment, the density analysis station also includes at leastone receiving transducer element positioned a defined/known distancefrom the transmitting transducer element for receiving the ultrasonicsignals from the transmitting transducer element.

In one embodiment, a conveyor system is provided to convey a sheet ofmaterial through the density analysis station. In one embodiment, as theconveyor system conveys the sheet of material through the densityanalysis station the transmitting transducer element is in contact witha first portion of a surface of the sheet of material and the receivingtransducer element is in contact with a second portion of the surface ofthe sheet of material at the defined/known distance from the firstportion of the surface of the sheet of material.

In one embodiment, ultrasonic signals are generated and transmitted fromthe transmitting transducer element into the sheet of material at thefirst portion of the surface of the sheet of material and pass throughthe sheet of material to be received by the receiving transducer elementat the second portion of the surface of the sheet of material.

In one embodiment, the method for determining the density of a sheet ofmaterial includes providing at least one magnetic force feedbackactuator positioner.

In one embodiment, the method for determining the density of a sheet ofmaterial includes operationally coupling the at least one magnetic forcefeedback actuator positioner to the transmitting transducer element. Inone embodiment, the at least one magnetic force feedback actuatorpositioner is used to apply and maintain a selected constant force onthe transmitting transducer element to maintain a constant pressure oftransmitting transducer element on the first portion of the surface ofthe sheet of material as the sheet of material is conveyed by theconveyor system through the density analysis station.

In one embodiment, a transmitting transducer element lever arm isprovided and operationally coupled to the at least one magnetic forcefeedback actuator positioner. In one embodiment, the transmittingtransducer element lever arm is also operationally coupled to thetransmitting transducer element. In this way the at least one magneticforce feedback actuator positioner applies and maintains a selectedforce on the transmitting transducer element through the transmittingtransducer element lever arm to keep a selected pressure between thetransmitting transducer element and the first portion of the surface ofthe sheet of material.

In one embodiment, at least one magnetic force feedback actuatorpositioner is provided and operationally coupled to the receivingtransducer element to apply and maintain a selected constant force onthe receiving transducer element. In this way a constant pressure of thereceiving transducer element on the second portion of the surface of thesheet of material is maintained as the sheet of material is conveyed bythe conveyor system through the density analysis station.

In one embodiment, a magnetic force feedback actuator positioner controlsystem is provided. In one embodiment, the at least one magnetic forcefeedback actuator positioner operationally coupled to the transmittingtransducer element and the at least one magnetic force feedback actuatorpositioner operationally coupled to the receiving transducer element arecontrolled to operate in tandem by a single magnetic force feedbackactuator positioner control system.

In one embodiment, a receiving transducer element lever arm is providedand operationally coupled to at least one magnetic force feedbackactuator positioner and the receiving transducer element lever arm isalso operationally coupled to the receiving transducer element. In thisway the at least one magnetic force feedback actuator positioner appliesand maintains a selected force on the receiving transducer elementthrough the receiving transducer element lever arm to keep a selectedpressure between the receiving transducer element and the second portionof the surface of the sheet of material.

In one embodiment, the transmitting transducer element for generatingand transmitting ultrasonic signals is contained in a transmittingtransducer wheel and as the conveyor system conveys the sheet ofmaterial through the density analysis station the transmittingtransducer wheel is in contact with a first portion of a surface of thesheet of material and the receiving transducer element is in contactwith a second portion of the surface of the sheet of material at thedefined/known distance from the first portion of the surface of thesheet of material. In one embodiment, ultrasonic signals generated andtransmitted from the transmitting transducer element in the transmittingtransducer wheel enter the sheet of material at the first portion of thesurface of the sheet of material and pass through the sheet of materialto be received by the receiving transducer element at the second portionof the surface of the sheet of material.

In one embodiment, the sheet of material is a sheet of wood product. Inone embodiment, the sheet of material is a sheet of veneer.

In one embodiment, density data obtained using the disclosed method fordetermining the density of a sheet of material is used to determine thestrength of the sheet of material. In one embodiment, density dataobtained using the disclosed method for determining the density of asheet of material is used, at least in part, to determine a gradeassigned to the sheet of material. In one embodiment, the grade assignedto the sheet of material is used to determine how the sheet of materialis used.

In one embodiment, a method for determining the density of a sheet ofmaterial is disclosed that includes providing at least one transmittingtransducer wheel. In one embodiment, the transmitting transducer wheelincludes a transmitting transducer element for generating andtransmitting ultrasonic signals.

In one embodiment, the disclosed method for determining the density of asheet of material includes at least one receiving transducer element. Inone embodiment, the disclosed method for determining the density of asheet of material includes positioning the receiving transducer elementa defined/known distance from the transmitting transducer wheel forreceiving the ultrasonic signals from the transmitting transducerelement in the transmitting transducer wheel.

In one embodiment, a conveyor system is provided. In one embodiment, theconveyor system is used to convey a sheet of material to thetransmitting transducer wheel and the receiving transducer element.

In one embodiment, as the conveyor system conveys the sheet of materialto the transmitting transducer wheel and the receiving transducerelement, the transmitting transducer wheel is in contact with a firstportion of a surface of the sheet of material and the receivingtransducer element is in contact with a second portion of the surface ofthe sheet of material at the same time and at the defined/known distancefrom the first portion of the surface of the sheet of material.

In one embodiment, the ultrasonic signals generated and transmitted fromthe transmitting transducer element of the transmitting transducer wheelenter the sheet of material at the first portion of the surface of thesheet of material and pass through the sheet of material to be receivedby the receiving transducer element at the second portion of the surfaceof the sheet of material.

In one embodiment, at least one magnetic force feedback actuatorpositioner is provided and operationally coupled to the transmittingtransducer wheel to apply a selected constant force on the transmittingtransducer wheel and maintain a constant pressure of the transmittingtransducer wheel on the first portion of the surface of the sheet ofmaterial as the sheet of material is conveyed by the conveyor systemthrough the density analysis station.

In one embodiment, at least one magnetic force feedback actuatorpositioner is provided and operationally coupled to the receivingtransducer element to apply a selected constant force on the receivingtransducer element and maintain a constant pressure of the receivingtransducer element on the second portion of the surface of the sheet ofmaterial as the sheet of material is conveyed by the conveyor systemthrough the density analysis station.

In one embodiment, a transmitting transducer element lever arm isprovided and operationally coupled to the at least one magnetic forcefeedback actuator positioner and the transmitting transducer wheel. Inthis way the at least one magnetic force feedback actuator positioner isused to apply a selected force on the transmitting transducer wheelthrough the transmitting transducer element lever arm to keep a selectedpressure between the transmitting transducer wheel and the first portionof the surface of the sheet of material.

In one embodiment, a receiving transducer element lever arm is providedand operationally coupled to the at least one magnetic force feedbackactuator positioner and the receiving transducer element. In this way,the at least one magnetic force feedback actuator positioner is used toapply a selected force on the receiving transducer element through thereceiving transducer element lever arm to keep a selected pressurebetween the receiving transducer element and the second portion of thesurface of the sheet of material.

In one embodiment, the sheet of material is a sheet of wood product. Inone embodiment, the sheet of material is a sheet of veneer.

In one embodiment, density data obtained using the disclosed method fordetermining the density of a sheet of material is used to determine thestrength of the sheet of material. In one embodiment, density dataobtained using the disclosed method for determining the density of asheet of material is used, at least in part, to determine a gradeassigned to the sheet of material. In one embodiment, the grade assignedto the sheet of material is used to determine how the sheet of materialis used.

In one embodiment, a method for determining the density of a sheet ofmaterial is disclosed that includes providing at least one transmittingtransducer wheel. In one embodiment, the transmitting transducer wheelincludes a transmitting transducer element for generating andtransmitting ultrasonic signals.

In one embodiment, the disclosed method for determining the density of asheet of material includes providing at least one receiving transducerelement. In one embodiment, the receiving transducer element ispositioned a defined/known distance from the transmitting transducerwheel for receiving the ultrasonic signals from the transmittingtransducer element in the transmitting transducer wheel.

In one embodiment, a conveyor system is provided and used to convey asheet of material to the transmitting transducer wheel and the receivingtransducer element. In one embodiment, as the conveyor system conveysthe sheet of material to the transmitting transducer wheel and thereceiving transducer element, the transmitting transducer wheel is incontact with a first portion of a surface of the sheet of material andthe receiving transducer element is in contact with a second portion ofthe surface of the sheet of material at the same time and at thedefined/known distance from the first portion of the surface of thesheet of material.

In one embodiment, the ultrasonic signals generated and transmitted fromthe transmitting transducer element of the transmitting transducer wheelenter the sheet of material at the first portion of the surface of thesheet of material and pass through the sheet of material to be receivedby the receiving transducer element at the second portion of the surfaceof the sheet of material.

In one embodiment, at least one transmitting transducer lift wheel isprovided and positioned such that the sheet of material passes betweenthe transmitting transducer wheel and the transmitting transducer liftwheel as the conveyor system conveys the sheet of material past thetransmitting transducer wheel and the receiving transducer element.

In one embodiment, at least one magnetic force feedback actuatorpositioner is provided and operationally coupled to the transmittingtransducer wheel to apply a selected constant force on the transmittingtransducer wheel and maintain a constant pressure of the transmittingtransducer wheel on the first portion of the surface of the sheet ofmaterial as the sheet of material is conveyed by the conveyor systempast the transmitting transducer wheel and the receiving transducerelement.

In one embodiment, at least one magnetic force feedback actuatorpositioner is provided and operationally coupled to the receivingtransducer element to apply a selected constant force on the receivingtransducer element to maintain a constant pressure of the receivingtransducer element on the second portion of the surface of the sheet ofmaterial as the sheet of material is conveyed by the conveyor systemthrough the past the transmitting transducer wheel and the receivingtransducer element.

In one embodiment, a receiving transducer wheel is provided. In oneembodiment, the receiving transducer element for receiving theultrasonic signals is contained in a receiving transducer wheel.

In one embodiment, at least one receiving transducer lift wheel isprovided and positioned such that the sheet of material passes betweenthe receiving transducer wheel and the receiving transducer lift wheelas the conveyor system conveys the sheet of material to the transmittingtransducer wheel and the receiving transducer wheel.

In one embodiment, a transmitting transducer element lever arm isprovided and operationally coupled to the at least one magnetic forcefeedback actuator positioner and the transmitting transducer wheel. Inthis way the at least one magnetic force feedback actuator positioner isused to apply a selected force on the transmitting transducer wheelthrough the transmitting transducer element lever arm to keep a selectedpressure between the transmitting transducer wheel and the first portionof the surface of the sheet of material.

In one embodiment, a receiving transducer element lever arm is providedand operationally coupled to the at least one magnetic force feedbackactuator positioner and the receiving transducer wheel. In this way, theat least one magnetic force feedback actuator positioner is used toapply a selected force on the receiving transducer wheel through thereceiving transducer element lever arm to keep a selected pressurebetween the receiving transducer wheel and the second portion of thesurface of the sheet of material.

In one embodiment, the sheet of material is a sheet of wood product. Inone embodiment, the sheet of material is a sheet of veneer.

In one embodiment, density data obtained using the disclosed method fordetermining the density of a sheet of material is used to determine thestrength of the sheet of material. In one embodiment, density dataobtained using the disclosed method for determining the density of asheet of material is used, at least in part, to determine a gradeassigned to the sheet of material. In one embodiment, the grade assignedto the sheet of material is used to determine how the sheet of materialis used.

Consequently, using the disclosed embodiments, many of the shortcomingsof prior art are minimized or by-passed/resolved.

The present invention has been described in particular detail withrespect to specific possible embodiments. Those of skill in the art willappreciate that the invention may be practiced in other embodiments. Forexample, the nomenclature used for components, capitalization ofcomponent designations and terms, the attributes, data structures, orany other programming or structural aspect is not significant,mandatory, or limiting, and the mechanisms that implement the inventionor its features can have various different names, formats, or protocols.Further, the system or functionality of the invention may be implementedvia various combinations of software and hardware, as described, orentirely in hardware elements. Also, particular divisions offunctionality between the various components described herein are merelyexemplary, and not mandatory or significant. Consequently, functionsperformed by a single component may, in other embodiments, be performedby multiple components, and functions performed by multiple componentsmay, in other embodiments, be performed by a single component.

In addition, the operations shown in the figures, or as discussedherein, are identified using a particular nomenclature for ease ofdescription and understanding, but other nomenclature is often used inthe art to identify equivalent operations.

Therefore, numerous variations, whether explicitly provided for by thespecification or implied by the specification or not, may be implementedby one of skill in the art in view of this disclosure.

What is claimed is:
 1. A method for determining the density of a sheet of material comprising: providing a density analysis station, the density analysis station including at least one transmitting transducer element, the transmitting transducer element generating and transmitting ultrasonic signals, the density analysis station including at least one receiving transducer element, the receiving transducer element being positioned a defined distance from the transmitting transducer element for receiving the ultrasonic signals from the transmitting transducer element; providing a conveyor system for conveying a sheet of material through the density analysis station such that as the conveyor system conveys the sheet of material through the density analysis station the transmitting transducer element is in contact with a first portion of a surface of the sheet of material and the receiving transducer element is in contact with a second portion of the surface of the sheet of material at the defined distance from the first portion of the surface of the sheet of material such that ultrasonic signals generated and transmitted from the transmitting transducer element enter the sheet of material at the first portion of the surface of the sheet of material and pass through the sheet of material to be received by the receiving transducer element at the second portion of the surface of the sheet of material; providing at least one magnetic force feedback actuator positioner; operationally coupling the at least one magnetic force feedback actuator positioner to the transmitting transducer element to apply a selected force on the transmitting transducer element to maintain a selected pressure of transmitting transducer element on the first portion of the surface of the sheet of material as the sheet of material is conveyed by the conveyor system through the density analysis station; and determining the density of the sheet of material based on the travel time of ultrasonic signals with shorter travel times indicating higher densities and longer travel times indicating lower densities.
 2. The method for determining the density of a sheet of material of claim 1 further comprising: providing a transmitting transducer element lever arm; operationally coupling the at least one magnetic force feedback actuator positioner to the transmitting transducer element lever arm; and operationally coupling the transmitting transducer element lever arm to the transmitting transducer element to apply a selected force on the transmitting transducer element to keep a selected pressure between the transmitting transducer element and the first portion of the surface of the sheet of material.
 3. The method for determining the density of a sheet of material of claim 1 further comprising: providing at least one magnetic force feedback actuator positioner; and operationally coupling the at least one magnetic force feedback actuator positioner to the receiving transducer element to apply a selected force on the receiving transducer element to maintain a selected pressure of the receiving transducer element on the second portion of the surface of the sheet of material as the sheet of material is conveyed by the conveyor system through the density analysis station.
 4. The method for determining the density of a sheet of material of claim 3 wherein the at least one magnetic force feedback actuator positioner operationally coupled to the transmitting transducer element and the at least one magnetic force feedback actuator positioner operationally coupled to the receiving transducer element are controlled to operate in tandem by a magnetic force feedback actuator positioner control system.
 5. The method for determining the density of a sheet of material of claim 1 further comprising: providing a receiving transducer element lever arm; operationally coupling the at least one magnetic force feedback actuator positioner to the receiving transducer element lever arm; and operationally coupling the receiving transducer element lever arm the receiving transducer element to apply a selected force on the receiving transducer element to keep a selected pressure between the receiving transducer element and the second portion of the surface of the sheet of material.
 6. The method for determining the density of a sheet of material of claim 1 wherein, the transmitting transducer element for generating and transmitting ultrasonic signals is contained in a transmitting transducer wheel, and further wherein, as the conveyor system conveys the sheet of material through the density analysis station the transmitting transducer wheel is in contact with a first portion of a surface of the sheet of material and the receiving transducer element is in contact with a second portion of the surface of the sheet of material at the defined distance from the first portion of the surface of the sheet of material such that ultrasonic signals generated and transmitted from the transmitting transducer element in the transmitting transducer wheel enter the sheet of material at the first portion of the surface of the sheet of material and pass through the sheet of material to be received by the receiving transducer element at the second portion of the surface of the sheet of material.
 7. The method for determining the density of a sheet of material of claim 1 wherein the sheet of material is a sheet of wood product.
 8. The method for determining the density of a sheet of material of claim 1 wherein the sheet of material is a sheet of veneer.
 9. A method for determining the density of a sheet of material comprising: providing at least one transmitting transducer wheel, the transmitting transducer wheel including a transmitting transducer element, the transmitting transducer element generating and transmitting ultrasonic signals; providing at least one receiving transducer element, the receiving transducer element being positioned a defined distance from the transmitting transducer wheel and receiving the ultrasonic signals from the transmitting transducer element in the transmitting transducer wheel; providing a conveyor system for conveying a sheet of material to the transmitting transducer wheel and the receiving transducer element such that as the conveyor system conveys the sheet of material to the transmitting transducer wheel and the receiving transducer element the transmitting transducer wheel is in contact with a first portion of a surface of the sheet of material and the receiving transducer element is in contact with a second portion of the surface of the sheet of material at the same time at the defined distance from the first portion of the surface of the sheet of material such that ultrasonic signals generated and transmitted from the transmitting transducer element of the transmitting transducer wheel enter the sheet of material at the first portion of the surface of the sheet of material and pass through the sheet of material to be received by the receiving transducer element at the second portion of the surface of the sheet of material; providing at least one magnetic force feedback actuator positioner operationally coupled to the transmitting transducer wheel to apply a selected force on the transmitting transducer wheel to maintain a selected pressure of the transmitting transducer wheel on the first portion of the surface of the sheet of material as the sheet of material is conveyed by the conveyor system through the density analysis station; providing at least one magnetic force feedback actuator positioner; operationally coupling the at least one magnetic force feedback actuator positioner to the receiving transducer element to apply a selected force on the receiving transducer element to maintain a selected pressure of the receiving transducer element on the second portion of the surface of the sheet of material as the sheet of material is conveyed by the conveyor system through the density analysis station; and determining the density of the sheet of material based on the travel time of ultrasonic signals with shorter travel times indicating higher densities and longer travel times indicating lower densities.
 10. The method for determining the density of a sheet of material of claim 9 further comprising: providing a transmitting transducer element lever arm; operationally coupling the at least one magnetic force feedback actuator positioner to the transmitting transducer element lever arm; and operationally coupling the transmitting transducer element lever arm to the transmitting transducer wheel to apply a selected force on the transmitting transducer wheel to keep a selected pressure between the transmitting transducer wheel and the first portion of the surface of the sheet of material.
 11. The method for determining the density of a sheet of material of claim 9 further comprising: providing a receiving transducer element lever arm; operationally coupling the at least one magnetic force feedback actuator positioner to the receiving transducer element lever arm; and operationally coupling the receiving transducer element lever arm to the receiving transducer element to apply a selected force on the receiving transducer element to keep a selected pressure between the receiving transducer element and the second portion of the surface of the sheet of material.
 12. The method for determining the density of a sheet of material of claim 9 wherein the sheet of material is a sheet of wood product.
 13. The method for determining the density of a sheet of material of claim 9 wherein the sheet of material is a sheet of veneer.
 14. A method for determining the density of a sheet of material comprising: providing at least one transmitting transducer wheel, the transmitting transducer wheel including a transmitting transducer element, the transmitting transducer element generating and transmitting ultrasonic signals; providing at least one receiving transducer element, the at least one receiving transducer element being positioned a defined distance from the transmitting transducer wheel for receiving the ultrasonic signals from the transmitting transducer element in the transmitting transducer wheel; providing a conveyor system for conveying a sheet of material to the transmitting transducer wheel and the receiving transducer element such that as the conveyor system conveys the sheet of material to the transmitting transducer wheel and the receiving transducer element the transmitting transducer wheel is in contact with a first portion of a surface of the sheet of material and the receiving transducer element is in contact with a second portion of the surface of the sheet of material at the same time at the defined distance from the first portion of the surface of the sheet of material such that ultrasonic signals generated and transmitted from the transmitting transducer element of the transmitting transducer wheel enter the sheet of material at the first portion of the surface of the sheet of material and pass through the sheet of material to be received by the receiving transducer element at the second portion of the surface of the sheet of material; providing at least one transmitting transducer lift wheel, the at least one transmitting transducer lift wheel positioned such that the sheet of material passes between the transmitting transducer wheel and the transmitting transducer lift wheel as the conveyor system conveys the sheet of material to the transmitting transducer wheel and the receiving transducer element; providing at least one magnetic force feedback actuator positioner; operationally coupling the at least one magnetic force feedback actuator positioner to the transmitting transducer wheel to apply a selected force on the transmitting transducer wheel to maintain a selected pressure of transmitting transducer wheel on the first portion of the surface of the sheet of material as the sheet of material is conveyed by the conveyor system past the transmitting transducer wheel and the receiving transducer element; providing at least one magnetic force feedback actuator positioner; operationally coupling the at least one magnetic force feedback actuator positioner to the receiving transducer element to apply a selected force on the receiving transducer element to maintain a selected pressure of the receiving transducer element on the second portion of the surface of the sheet of material as the sheet of material is conveyed by the conveyor system past the transmitting transducer wheel and the receiving transducer element; and determining the density of the sheet of material based on the travel time of ultrasonic signals with shorter travel times indicating higher densities and longer travel times indicating lower densities.
 15. The method for determining the density of a sheet of material of claim 14 wherein the receiving transducer element for receiving the ultrasonic signals is contained in a receiving transducer wheel.
 16. The method for determining the density of a sheet of material of claim 15 further comprising: providing at least one receiving transducer lift wheel, the at least one receiving transducer lift wheel positioned such that the sheet of material passes between the receiving transducer wheel and the receiving transducer lift wheel as the conveyor system conveys the sheet of material to the transmitting transducer wheel and the receiving transducer wheel.
 17. The method for determining the density of a sheet of material of claim 14 further comprising: providing a transmitting transducer element lever arm; operationally coupling the at least one magnetic force feedback actuator positioner to the transmitting transducer element lever arm; and operationally coupling the transmitting transducer element lever arm operationally coupled to the transmitting transducer wheel to apply a selected force on the transmitting transducer wheel to keep a selected pressure between the transmitting transducer wheel and the first portion of the surface of the sheet of material.
 18. The method for determining the density of a sheet of material of claim 16 further comprising: providing a receiving transducer element lever arm; operationally coupling the at least one magnetic force feedback actuator positioner to the receiving transducer element lever arm; and operationally coupling the receiving transducer element lever arm to the receiving transducer wheel to apply a selected force on the receiving transducer wheel to keep a selected pressure between the receiving transducer wheel and the second portion of the surface of the sheet of material.
 19. The method for determining the density of a sheet of material of claim 14 wherein the sheet of material is a sheet of wood product.
 20. The method for determining the density of a sheet of material of claim 14 wherein the sheet of material is a sheet of veneer. 